The region will feature three separate availability zones for increased fault tolerance.
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Baird L. The Swirlds Hashgraph Consensus Algorithm: Fair, Fast, Byzantine Fault Tolerance, Swirlds Tech Report SWIRLDS-TR-2016-01 (2016); 22.
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The practical byzantine fault tolerance algorithm (PBFT) was designed as a solution to a problem presented in the form of a fun parable.
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The Resilient File System (ReFS), as the name implies, is meant to provide an extra level of data availability, resilience and fault-tolerance.
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TON's third generation blockchain will be based on a dynamic 'proof of stake' secured by multiple parties with a high degree of fault tolerance.
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The Libra Blockchain is designed like a true blockchain, with a Byzantine Fault Tolerance approach, the use of Merkle trees to guarantee the integrity and a network of nodes.
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Fault tolerance, creating high-quality qubits (often from many physical qubits) that don't error out, is what many are focused on as much as they are on the number of qubits.
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On the other hand, NEO uses a delegated Byzantine Fault Tolerance (dBFT) consensus mechanism that makes it possible to sync up the network a lot quicker without spending a lot of energy.
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Thanks to a Byzantine Fault Tolerance system, just two-thirds of the nodes must come to consensus that the transaction is legitimate for it to be executed and written to the blockchain.
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There are many methods of finding consensus in a distributed system, but two stand out that are most compelling: the practical byzantine fault tolerance algorithm (PBFT), and the proof-of-work algorithm (PoW).
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One issue is that only two out of three parachutes deployed, which will have to be investigated, but the actual fault tolerance defined by NASA here allows and anticipates that as a possibility.
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Not only does that give their mission fault tolerance (one of the craft could totally fail and the other would be unaffected) but it could offer opportunities for unique data-gathering techniques like stereo spectrography.
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"As monolithic applications are decomposed into microservices, software teams have to worry about the challenges inherent in integrating services in distributed systems: they must account for service discovery, load balancing, fault tolerance, end-to-end monitoring, dynamic routing for feature experimentation, and perhaps most important of all, compliance and security," the Istio team explains.
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If you're not, say, a computer scientist or a mathematician, the deeper you get into the esoterica of distributed ledgers, consensus algorithms, hash functions, zero-knowledge proofs, byzantine-fault-tolerance theory, and so on—the farther you travel from the familiar terrain of "the legacy world," where, one blockchain futurist told me, pityingly, I live—the better the chance you have of bumping up against the limits of your intelligence.
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This provides full fault tolerance for thruster or propellant circuit failure.
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In the early 1980s, Jean- Claude Laprie thus chose dependability as the term to encompass studies of fault tolerance and system reliability without the extension of meaning inherent in reliability.J.C. Laprie. "Dependable Computing and Fault Tolerance: Concepts and terminology," in Proc. 15th IEEE Int. Symp.
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Byzantine fault tolerance (BFT) is the dependability of a fault-tolerant computer system to such conditions.
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It is due to the high overhead and the unhandiness of the previous fault-tolerance systems.
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As Paxos's point is to ensure fault tolerance and it guarantees safety, it cannot also guarantee liveness.
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Sales of the Itanium- based systems ended in July 2020. Early NonStop applications had to be specifically coded for fault-tolerance. That requirement was removed in 1983 with the introduction of the Transaction Monitoring Facility (TMF), which handles the various aspects of fault tolerance on the system level.
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Self-stabilization is a concept of fault-tolerance in distributed systems. Given any initial state, a self-stabilizing distributed system will end up in a correct state in a finite number of execution steps. At first glance, the guarantee of self stabilization may seem less promising than that of the more traditional fault-tolerance of algorithms, that aim to guarantee that the system always remains in a correct state under certain kinds of state transitions. However, that traditional fault tolerance cannot always be achieved.
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XtreemFS' outstanding feature is full (all components) and real (all failure scenarios, including network partitions) fault tolerance, while maintaining POSIX file system semantics. Fault-tolerance is achieved by using Paxos-based lease negotiation algorithms and is used to replicate files and metadata. SSL and X.509 certificates support make XtreemFS usable over public networks.
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The virtual synchrony model is sometimes used to endow event notification systems, and publish-subscribe systems, with stronger fault- tolerance and consistency guarantees.
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Byzantine fault tolerance is only concerned about broadcast correctness, that is, the property that when one component broadcasts a single consistent value to other components (i.e sends the same value to the other components), they all receive exactly the same value, or in the case that the broadcaster is not consistent, the other components agree on a common value. This kind of fault tolerance does not encompass the correctness of the value itself; for example, an adversarial component that deliberately sends an incorrect value, but sends that same value consistently to all components, will not be caught in the Byzantine fault tolerance scheme.
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Though the codes typically have no Hamiltonian to provide suppression of errors, fault-tolerance would be provided by the underlying quantum error correcting code.
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If desired, users can dedicate one process per node to overlap fault tolerance workload and scientific computation, so that post-checkpoint tasks are executed asynchronously.
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92 – 171, 2012. fault tolerance,F.J. Ros, P.M. Ruiz, "Five nines of southbound reliability in software defined networks," proceedings of HotSDN’14, 2014. and application requirements.
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Replication in computing involves sharing information so as to ensure consistency between redundant resources, such as software or hardware components, to improve reliability, fault-tolerance, or accessibility.
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The save mechanism provides fault tolerance. Coordination is required to produce a consistent snapshot of all ACMs, translators and simulations for a particular value of simulation time.
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Fault-tolerance against failure of a constituent cloud. ; Crashplan : Unlimited destinations. Data de-duplication; block-level incremental. Can run server-free, exchanging backup space with friends and family.
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One example of BFT in use is bitcoin, a peer-to-peer digital cash system. The bitcoin network works in parallel to generate a blockchain with proof-of-work allowing the system to overcome Byzantine failures and reach a coherent global view of the system's state. Some aircraft systems, such as the Boeing 777 Aircraft Information Management System (via its ARINC 659 SAFEbus network), the Boeing 777 flight control system, and the Boeing 787 flight control systems use Byzantine fault tolerance; because these are real-time systems, their Byzantine fault tolerance solutions must have very low latency. For example, SAFEbus can achieve Byzantine fault tolerance within the order of a microsecond of added latency.
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His most cited paper, "Finding Response Times in a Real-Time System", with over a thousand citations on Google Scholar, was joint work with Paritosh Pandya, published in The Computer Journal in 1986. Joseph's joint work with Zhiming Liu on fault tolerance gives a formal model that precisely defines the notions of fault, error, failure and fault-tolerance, and their relationships. It also provided the properties that models fault-affected programs and fault-tolerant programs in terms of transformations. Together, they proposed a design process for fault-tolerant systems from requirement specifications and analysis, fault environment identification and analysis, specification of fault-affected design and verification of fault-tolerance for satisfaction of the requirements specification.
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This also determines the choice of routing table entries. Each peer, for each level of the trie, maintains autonomously routing entries chosen randomly from the complementary sub-trees. In fact, multiple entries are maintained for each level at each peer to provide fault-tolerance (as well as potentially for query-load management). For diverse reasons including fault-tolerance and load-balancing, multiple peers are responsible for each leaf node in the P-Grid tree.
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Mimic Defense is a kind of architectural technology derived from fault tolerance in the field of reliability. Its fundamental form evolved from static DRS served as fault tolerance to DHR applied in intrusion tolerance. However, MTD is inspired by the idea of Encryption and Scrambler, which typically makes the instruction, address, or data of systems dynamic, random and diverse in order to increase the level of efforts required to achieve a successful compromise.
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Multipath routing is a routing technique simultaneously using multiple alternative paths through a network. This can yield a variety of benefits such as fault tolerance, increased bandwidth, or improved security.
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In his report on Dijkstra's work on self-stabilizing distributed systems, Lamport regard it to be 'a milestone in work on fault tolerance' and 'a very fertile field for research'.
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Situations where resource sharing becomes an issue, or where higher fault tolerance is needed also find aid in distributed networking. Distributed networking is also very supportive of higher levels of anonymity.
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ODBMS, "Polyglot Persistence or Multiple Data Models?" JSON documents, graphs, and relational tables can all be implemented in a manner that inherits the horizontal scalability and fault-tolerance of the underlying data store.
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Software fault tolerance is the ability of computer software to continue its normal operation despite the presence of system or hardware faults. Fault- tolerant software has the ability to satisfy requirements despite failures.
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Determinism is an ideal characteristic for providing fault-tolerance. Intuitively, if multiple copies of a system exist, a fault in one would be noticeable as a difference in the State or Output from the others. A little deduction shows the minimum number of copies needed for fault-tolerance is three; one which has a fault, and two others to whom we compare State and Output. Two copies are not enough as there is no way to tell which copy is the faulty one.
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It also enables a significant reduction in engine hours. Approval of a closed bus requires validation of the fault tolerance of the connected system, including live short-circuit testing of worst-case failure modes.
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Despite the analogy, a Byzantine failure is not necessarily a security problem involving hostile human interference: it can arise purely from electrical or software faults. The terms fault and failure are used here according to the standard definitions originally created by a joint committee on "Fundamental Concepts and Terminology" formed by the IEEE Computer Society's Technical Committee on Dependable Computing and Fault-Tolerance and IFIP Working Group 10.4 on Dependable Computing and Fault Tolerance. A version of these definitions is also described in the Dependability Wikipedia page.
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Some spacecraft flight systems such as that of the SpaceX Dragon consider Byzantine fault tolerance in their design. Byzantine fault tolerance mechanisms use components that repeat an incoming message (or just its signature) to other recipients of that incoming message. All these mechanisms make the assumption that the act of repeating a message blocks the propagation of Byzantine symptoms. For systems that have a high degree of safety or security criticality, these assumptions must be proven to be true to an acceptable level of fault coverage.
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Sector is a user space file system which relies on the local/native file system of each node for storing uploaded files. Sector provides file system-level fault tolerance by replication, thus it does not require hardware fault tolerance such as RAID, which is usually very expensive. Sector does not split user files into blocks; instead, a user file is stored intact on the local file system of one or more slave nodes. This means that Sector has a file size limitation that is application specific.
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"Securing skeletal systems with limited performance penalty: the muskel experience." Journal of Systems Architecture, 2008. and resource discovery, load balancing, and fault tolerance when interfaced with Java / Jini Parallel Framework (JJPF),M. Danelutto and P. Dazzi.
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A virtual IP address (VIP or VIPA) is an IP address that doesn't correspond to an actual physical network interface. Uses for VIPs include network address translation (especially, one-to-many NAT), fault-tolerance, and mobility.
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Narasimhan was born in India and lived in Zambia, in Africa. She attended the University of California, Santa Barbara, where she completed her Ph.D. in Electrical and Computer Engineering and received the 2000 Lancaster Best Doctoral Dissertation Award for her research in the area of developing mechanisms to provide fault-tolerance transparently (i.e., with no code modifications) to existing distributed applications. In 2001, she moved to Pittsburgh to join Carnegie Mellon University as a faculty member, where her academic interests include dependable distributed systems, fault-tolerance, embedded systems, mobile systems and sports technology.
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A young designer, Jeff Childress, created an autonomous radio base-station controller, known as the GETC (General Electric Trunking Card). The GETC was a general-purpose controller with input/output optimized for radio system applications. Childress and the team demonstrated that a smart controller could be adapted to a variety of applications, but his interest was really in fault tolerance. The competition dealt with fault tolerance by means of the "brute force and ignorance" approach, deploying double the hardware for their controllers, and interconnecting them with massive and problematic relay banks .
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Geoplexing is a computer science term relating to the duplication of computer storage and applications within a server farm over geographically diverse locations for the purpose of fault tolerance. The name comes from a contraction of geographical multiplex.
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Major problems faced by the three-tier architecture include, scalability, fault tolerance, energy efficiency, and cross-sectional bandwidth. The three-tier architecture uses enterprise-level network devices at the higher layers of topology that are very expensive and power hungry.
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Servers may access storage from multiple storage devices over the network as well. SANs are often designed with dual fabrics to increase fault tolerance. Two completely separate fabrics are operational and if the primary fabric fails, then the second fabric becomes the primary.
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When the destination identifies a lack of heartbeat messages during an anticipated arrival period, the destination may determine that the originator has failed, shutdown, or is generally no longer available. Heartbeat messages may be used for high-availability and fault tolerance purposes.
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Virtual synchrony was also used in developing the New York Stock Exchange fault-tolerance architecture, the French Air Traffic Control System, the US Navy AEGIS system, IBM's Business Process replication architecture for WebSphere and Microsoft's Windows Clustering architecture for Windows Longhorn enterprise servers.
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There are open source codes to implement BRS encoding written in C and available on Github. In the design and implementation of a distributed storage system, we can use BRS encoding to store data and to achieve the system's own fault tolerance.
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Brian Randell (born 1936) is a British computer scientist, and Emeritus Professor at the School of Computing, Newcastle University, United Kingdom. He specialises in research into software fault tolerance and dependability, and is a noted authority on the early pre-1950 history of computing hardware.
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To provide better control over transaction processing, significant improvements in fault tolerance, and richer support for networking, CCI developed PERPOS, a Unix derivative that provided integrated support for real-time transaction processing, load balancing, and fault tolerant features such as hot and cold standby.
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NonStop SQL is a commercial relational database management system that is designed for fault tolerance and scalability, currently offered by Hewlett Packard Enterprise. The latest version is SQL/MX 3.4. The product was originally developed by Tandem Computers. Tandem was acquired by Compaq in 1997.
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Windows Storage Server 2003 NAS equipment can be headless, which means that they are without any monitors, keyboards or mice, and are administered remotely. Such devices are plugged into any existing IP network and the storage capacity is available to all users. Windows Storage Server 2003 can use RAID arrays to provide data redundancy, fault-tolerance and high performance. Multiple such NAS servers can be clustered to appear as a single device, which allows responsibility for serving clients to be shared in such a way that if one server fails then other servers can take over (often termed a failover) which also improves fault-tolerance.
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Because the reliability of the system depends on quick replacement of the bad drive so the array can rebuild, it is common to include hot spares that can immediately start rebuilding the array upon failure. However, this does not address the issue that the array is put under maximum strain reading every bit to rebuild the array at the time when it is most vulnerable. RAID 50 improves upon the performance of RAID 5 particularly during writes, and provides better fault tolerance than a single RAID level does. This level is recommended for applications that require high fault tolerance, capacity and random access performance.
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Fujitsu Limited developed a 6D torus computer model called "Tofu". In their model, a 6D torus can achieve 100 GB/s off-chip bandwidth, 12 times higher scalability than a 3D torus, and high fault tolerance. The model is used in the K computer and Fugaku.
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Starting in the 1970s, Randell "set up the project that initiated research into the possibility of software fault tolerance, and introduced the recovery block concept. Subsequent major developments included the Newcastle Connection, and the prototype distributed Secure System".Brian Randell at School of Computing Science. Last updated March 2008.
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The one-sided communication of the BSP model requires barrier synchronization. Barriers are potentially costly, but avoid the possibility of deadlock or livelock, since barriers cannot create circular data dependencies. Tools to detect them and deal with them are unnecessary. Barriers also permit novel forms of fault tolerance.
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Xenbase runs in a cloud environment. Its virtual machines are running in a VMware vSphere environment on two servers, with automatic load balancing and fault tolerance. Xenbase software uses Java, JSP, JavaScript, AJAX, XML, and CSS. It also uses IBM's WebSphere Application Server and the IBM DB2 database.
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Artificial Immune Systems and Their Applications. Springer, 1998 These include distinguishing between self and nonself,de Castro, L., Timmis, J. Artificial Immune Systems: A New Computational Intelligence Approach. Springer, 2002. neutralization of nonself pathogens (viruses, bacteria, fungi, and parasites), learning, memory, associative retrieval, self-regulation, and fault-tolerance.
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Because RocksDB can write to disk, the maintained state can be larger than available main memory. For fault-tolerance, all updates to local state stores are also written into a topic in the Kafka cluster. This allows recreating state by reading those topics and feed all data into RocksDB.
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Diagram of a RAID 0 setup RAID 0 (also known as a stripe set or striped volume) splits ("stripes") data evenly across two or more disks, without parity information, redundancy, or fault tolerance. Since RAID 0 provides no fault tolerance or redundancy, the failure of one drive will cause the entire array to fail; as a result of having data striped across all disks, the failure will result in total data loss. This configuration is typically implemented having speed as the intended goal. RAID 0 is normally used to increase performance, although it can also be used as a way to create a large logical volume out of two or more physical disks.
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The Datacenter edition, like the Enterprise edition, supports 8-node clustering. Clustering increases availability and fault tolerance of server installations by distributing and replicating the service among many servers. This edition supports clustering with each cluster having its own dedicated storage, or with all cluster nodes connected to a common SAN.
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CCT is composed of eight design principles: (1) Collaboration Requirement Planning (CRP); (2) e-Work Parallelism (EWP); (3) Keep It Simple, System (KISS); (4) Conflict/Error Detection and Prevention (CEDP); (5) Fault Tolerance by Teaming (FTT); (6) Association/Dissociation (AD); (7) Dynamic Lines of Collaboration (DLOC); (8) Best Matching (BM).
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To facilitate fault tolerance, each chunk is replicated onto multiple (default, three) chunk servers. A chunk is available on at least one chunk server. The advantage of this scheme is simplicity. The master is responsible for allocating the chunk servers for each chunk and is contacted only for metadata information.
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2198 - 2215, May 2016 Some examples of DSP cores are FIR filter, IIR filter, FFT, DFT, JPEG, HWT etc. Few of the most important properties of a DSP core watermarking process are as follows: (a) Low embedding cost (b) Secret mark (c) Low creation time (d) Strong tamper tolerance (e) Fault tolerance.
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Fault avoidance covers proactive measures taken to minimize the occurrence of faults. These proactive measures can be in the form of transactions, replication and backups. Fault tolerance is the ability of a system to continue operation in the presence of a fault. In the event, the system should detect and recover full functionality.
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Vector-Field ConsistencyDesignation coined by L. Veiga. is a consistency model for replicated data (for example, objects), initially described in a paper which was awarded the best-paper prize in the ACM/IFIP/Usenix Middleware Conference 2007. It has since been enhanced for increased scalability and fault-tolerance in a recent paper.
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Checkpointing is a technique that provides fault tolerance for computing systems. It basically consists of saving a snapshot of the application's state, so that applications can restart from that point in case of failure. This is particularly important for the long running applications that are executed in the failure-prone computing systems.
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Evolvable hardware (EH) is a field focusing on the use of evolutionary algorithms (EA) to create specialized electronics without manual engineering. It brings together reconfigurable hardware, evolutionary computation, fault tolerance and autonomous systems. Evolvable hardware refers to hardware that can change its architecture and behavior dynamically and autonomously by interacting with its environment.
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Kalman filters are an important filtering technique for building fault-tolerance into a wide range of systems, including real-time imaging. The ordinary Kalman filter is generally optimal for many systems. However, an optimal Kalman filter is not stable (i.e. reliable) if Kalman's observability and controllability conditions are not continuously satisfied (Kalman, 1960).
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Proceedings of SIGIR, 405-411, 1990. ;Fault tolerance : How important it is for the service to be reliable. Issues include dealing with index corruption, determining whether bad data can be treated in isolation, dealing with bad hardware, partitioning, and schemes such as hash- based or composite partitioning,Linear Hash Partitioning. MySQL 5.1 Reference Manual.
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Another middleware service is that of providing for data transport or data transfer. Data transport will encompass multiple functions that are not just limited to the transfer of bits, to include such items as fault tolerance and data access.Coetzee, Serena. Reference model for a data grid approach to address data in a dynamic SDI p.
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CapROS ("Capability-based Reliable Operating System") is an open source operating system. It is a pure capability-based system that features automatic persistence of data and processes, even across system reboots. Capability systems naturally support the principle of least authority, which improves security and fault tolerance. CapROS is an evolution of the EROS system.
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P. Mehra and S. Fineberg, "Fast and flexible persistence: the magic potion for fault-tolerance, scalability and performance in online data stores," 18th International Parallel and Distributed Processing Symposium, 2004. Proceedings., Santa Fe, NM, USA, 2004, pp. 206-. doi: 10.1109/IPDPS.2004.1303232 It can be provided using microprocessor memory instructions, such as load and store.
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P. polycephalum created a network similar to the existing train system, and "with comparable efficiency, fault tolerance, and cost". Similar results have been shown based on road networks in the United Kingdom and the Iberian peninsula (i.e., Spain and Portugal). P. polycephalum not only can solve these computational problems but also exhibits some form of memory.
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This allowed users to tailor their systems to their needs, even on the fly. The BiiN systems also provided two versions of fault tolerance. In fault-checking mode, processors were paired so that they could check one another's calculations. In event of an error, the processors would stop, and the circuitry would determine which was faulty.
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Prior to control reconfiguration, it must be at least determined whether a fault has occurred (fault detection) and if so, which components are affected (fault isolation). Preferably, a model of the faulty plant should be provided (fault identification). These questions are addressed by fault diagnosis methods. Fault accommodation is another common approach to achieve fault tolerance.
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The Brooks–Iyengar hybrid algorithm for distributed control in the presence of noisy data combines Byzantine agreement with sensor fusion. It bridges the gap between sensor fusion and Byzantine fault tolerance. This seminal algorithm unified these disparate fields for the first time. Essentially, it combines Dolev's algorithm for approximate agreement with Mahaney and Schneider's fast convergence algorithm (FCA).
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Euro-Par 2004 Parallel Processing, volume 3149 of LNCS, pages 596–605. Springer, 2004. a hierarchical and fault-tolerant Distributed Shared Memory (DSM) system is used to interconnect streams of data between processing elements by providing a repository with: get/put/remove/execute operations. Research around AdHoc has focused on transparency, scalability, and fault-tolerance of the data repository.
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One implementor reduced power usage by 46% with a stack cache and automated insertion of clock gating. The power usage was then roughly equivalent to the small open-source Amber core, which implements the ARM v2a architecture. The parts of the ZPU that would be most aided by fault-tolerance are the address bus, stack pointer and program counter.
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TTEthernet (i.e. Ethernet switch with SAE AS6802) integrates a model of fault- tolerance and failure management . TTEthernet switch can implement a reliable redundancy management and dataflow (datastream) integration to assure message transmission even in case of a switch failure. The SAE AS6802 implemented on an Ethernet switch supports the design of synchronous system architectures with defined fault-hypothesis.
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In a telecommunication network, a ring network affords fault tolerance to the network because there are two paths between any two nodes on the network. Ring protection is the system used to assure communication continues in the event of failure of one of the paths. There are two widely used protection architectures: 1+1 protection and 1:1 protection.
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Solr (pronounced "solar") is an open-source enterprise-search platform, written in Java, from the Apache Lucene project. Its major features include full-text search, hit highlighting, faceted search, real-time indexing, dynamic clustering, database integration, NoSQL features and rich document (e.g., Word, PDF) handling. Providing distributed search and index replication, Solr is designed for scalability and fault tolerance.
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Ant robotics is a special case of swarm robotics. Swarm robots are simple (and hopefully, therefore cheap) robots with limited sensing and computational capabilities. This makes it feasible to deploy teams of swarm robots and take advantage of the resulting fault tolerance and parallelism. Swarm robots cannot use conventional planning methods due to their limited sensing and computational capabilities.
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Irith Pomeranz is an Israeli electrical engineer known for her research in circuit testing and fault tolerance. She is a professor of electrical and computer engineering at Purdue University and a Fellow of the IEEE. As of 2019, her current research includes: Test generation, design for testability, built in self test and diagnosis of integrated circuits.
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If these switches are from a different vendor, they may use a different proprietary protocol between themselves. But "virtual" switches A and B still communicate using LACP. # Crossing two links to form an X makes no difference logically, any more than crossing links in a normal LAG would. However, physically it provides much improved fault tolerance (high availability).
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Robert Tienwen Chien (November 20, 1931 – December 8, 1983) was an American computer scientist concerned largely with research in information theory, fault-tolerance, and artificial intelligence (AI), director of the Coordinated Science Laboratory (CSL) at the University of Illinois at Urbana–Champaign, and known for his invention of the Chien search and seminal contributions to the PMC model in system level fault diagnosis.
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AppScale decouples app logic from its service ecosystem to give developers and cloud administrators control over app deployment, data storage, resource use, backup, and migration.. AppScale Systems (2018-03-09). Retrieved on 2018-03-09. AppScale includes high-level APIs for persistence, asynchronous execution, distributed memory cache, user authentication, and more. It handles service discovery, load-balancing, fault- tolerance, and auto-scaling.
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Multiple static routes, on a switch-by-switch basis, could be defined for fault tolerance. Network management functions continued to run on Prime minicomputers. Telenet initially used a proprietary virtual connection host interface. Roberts and Barry Wessler joined the international effort to standardize the a protocol for packet-switched data communication based on virtual circuits shortly before it was finalized.
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With this approach, the method of delivery of list of IPs to the client can vary, and may be implemented as a DNS list (delivered to all the clients without any round-robin), or via hardcoding it to the list. If a "smart client" is used, detecting that randomly selected server is down and connecting randomly again, it also provides fault tolerance.
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Installations in the USAF Semi-Automatic Ground Environment (SAGE) air defense network were configured as duplex systems, using a pair of AN/FSQ-7 computers to provide fault tolerance. One was active at any time, the other on standby. The standby system copied data from the active system to minimize switchover time if needed. A scheduled switchover took place every day.
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FTI is a library that aims to provide computational scientists with an easy way to perform checkpoint/restart in a scalable fashion.Bautista-Gomez, L., Tsuboi, S., Komatitsch, D., Cappello, F., Maruyama, N., & Matsuoka, S. (2011, November). FTI: high performance fault tolerance interface for hybrid systems. In Proceedings of 2011 International Conference for High Performance Computing, Networking, Storage and Analysis (p. 32). ACM.
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A multiprocessor system is defined as "a system with more than one processor", and, more precisely, "a number of central processing units linked together to enable parallel processing to take place". The key objective of a multiprocessor is to boost a system's execution speed. The other objectives are fault tolerance and application matching. The term "multiprocessor" can be confused with the term "multiprocessing".
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FileX is the embedded file system for ThreadX. FileX supports FAT12, 16, 32, and exFAT formats. The latter extends FAT file sizes beyond 4 GB, which is especially useful for video files, and it requires license directly from Microsoft for use. FileX also offers fault tolerance and supports direct NOR and NAND flash memory media through a flash wear leveling product called LevelX.
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Myrinet includes a number of fault-tolerance features, mostly backed by the switches. These include flow control, error control, and "heartbeat" monitoring on every link. The "fourth-generation" Myrinet, called Myri-10G, supported a 10 Gbit/s data rate and can use 10 Gigabit Ethernet on PHY, the physical layer (cables, connectors, distances, signaling). Myri-10G started shipping at the end of 2005.
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OrientDB Community Edition is free for any use (Apache 2 license). The open source software is built upon by a community of developers. Features such as horizontal scaling, fault tolerance, clustering, sharding, and replication aren’t disabled in the OrientDB Community Edition. OrientDB Enterprise Edition is the commercial extension of OrientDB Community Edition created to handle more robust and demanding use cases.
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The system contains both a leaf set of neighbor nodes, which provides fault tolerance and a probabilistic invariant of constant routing progress, and a PRR-style routing table to improve routing time to a logarithmic factor of network size. Chimera is currently being used in industry labs, as part of research done by the U.S. Department of Defense, and by startup companies.
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Hashgraph is a distributed ledger technology developed by Leemon Baird, the co-founder and CTO of Swirlds, in 2016. It is an asynchronous Byzantine Fault Tolerance (aBFT) consensus algorithm that they consider capable of securing the platform against attacks. It does not use miners to validate transactions, and uses directed acyclic graphs for time-sequencing transactions without bundling them into blocks.
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She has served as co-director of the CyLab Mobility Research Center at Carnegie Mellon University and headed the Intel Science and Technology Centre in Embedded Computing at Carnegie Mellon University. She has written and published more than 150 research papers on distributed systems and fault tolerance, research that led to the development of the Fault Tolerant CORBA industrial standard. With her Ph.D. students at Carnegie Mellon, she has worked on research in the areas of failure diagnosis, mobile edge computing, adaptive fault-tolerance, live software upgrades, static analysis, and machine-learning to solve systems problems. Her interest in computers and technology for sports led her to develop mobile apps bringing real-time statistics, multimedia, streaming radio, social media, and live video feeds to teams in the NFL, NBA, NHL, NRL, AFL, NBL, CFL and other sports leagues around the world.
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Many distributed filesystems use replication to ensure fault tolerance and avoid a single point of failure. Many commercial synchronous replication systems do not freeze when the remote replica fails or loses connection – behaviour which guarantees zero data loss – but proceed to operate locally, losing the desired zero recovery point objective. Techniques of wide-area network (WAN) optimization can be applied to address the limits imposed by latency.
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PCI Express is targeted at the host to peripheral market, as opposed to embedded systems. Unlike RapidIO, PCIe is not optimized for peer-to-peer multi processor networks. PCIe is ideal for host to peripheral communication. PCIe does not scale as well in large multiprocessor peer-to-peer systems, as the basic PCIe assumption of a "root complex" creates fault tolerance and system management issues.
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N-version programming (NVP), also known as multiversion programming or multiple-version dissimilar software, is a method or process in software engineering where multiple functionally equivalent programs are independently generated from the same initial specifications.N-Version Programming: A Fault- Tolerance Approach to Reliability of Software Operation, Liming Chen; Avizienis, A., Fault-Tolerant Computing, 1995, ' Highlights from Twenty-Five Years'., Twenty-Fifth International Symposium on, Vol., Iss.
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In contrast, the performance of conventional multiprocessor systems is limited by the speed of some shared memory, bus, or switch. Adding more than 4–8 processors in that manner gives no further system speedup. NonStop systems have more often been bought to meet scaling requirements than for extreme fault tolerance. They compete well against IBM's largest mainframes, despite being built from simpler minicomputer technology.
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Rebuilding an array requires reading all data from all disks, opening a chance for a second drive failure and the loss of the entire array. RAID 6 consists of block-level striping with double distributed parity. Double parity provides fault tolerance up to two failed drives. This makes larger RAID groups more practical, especially for high-availability systems, as large-capacity drives take longer to restore.
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Version 3 was released in March 1993, and supported fault tolerance and better portability. PVM was a step towards modern trends in distributed processing and grid computing but has, since the mid-1990s, largely been supplanted by the much more successful MPI standard for message passing on parallel machines. PVM is free software, released under both the BSD License and the GNU General Public License.
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Xsan is a complete SAN solution that includes the metadata controller software, the file system client software, and integrated setup, management and monitoring tools. Xsan has all the normal features to be expected in an enterprise shared disk file system, including support for large files and file systems, multiple mounted file systems, metadata controller failover for fault tolerance, and support for multiple operating systems.
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Both DPT and SRP are independent of their physical layers. This means that the DPT protocol can operate above several physical mediums such as SONET/SDH, Gigabit Ethernet, and others. As aforementioned, DPT is composed of two rings for fault tolerance and increased throughput. The method for switching between these two rings in the event of a failure is called Intelligent Protection Switching, or IPS.
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In Windows NT 4 domains, the backup domain controller (BDC) is a computer that has a copy of the user accounts database. Unlike the accounts database on the PDC, the BDC database is a read-only copy. When changes are made to the master accounts database on the PDC, the PDC pushes the updates down to the BDCs. These additional domain controllers exist to provide fault tolerance.
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Because they provide a way of producing the same vector within a space, signals can be encoded in various ways. This facilitates fault tolerance and resilience to a loss of signal. Finally, redundancy can be used to mitigate noise, which is relevant to the restoration, enhancement, and reconstruction of signals. In signal processing, it is common to assume the vector space is a Hilbert space.
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Samza allows users to build stateful applications that process data in real-time from multiple sources including Apache Kafka. Samza provides fault tolerance, isolation and stateful processing. Unlike batch systems such as Apache Hadoop or Apache Spark, it provides continuous computation and output, which result in sub- second response times. There are many players in the field of real-time stream processing and Samza is one of the mature products.
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Distributed OS can provide the necessary resources and services to achieve high levels of reliability, or the ability to prevent and/or recover from errors. Faults are physical or logical defects that can cause errors in the system. For a system to be reliable, it must somehow overcome the adverse effects of faults. The primary methods for dealing with faults include fault avoidance, fault tolerance, and fault detection and recovery.
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Some proposed QoS routing algorithms do consider multiple metrics, but without considering cross-layer cooperation. Multipath routing is another type of QoS routing that has received much attention, since it can provide load balancing, fault tolerance, and higher aggregate bandwidth. Although this approach decreases packet loss and end-to-end delay, it is only efficient and reliable if a relationship can be found between the number of paths and QoS constraints.
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As an example, GridFTP provides for fault tolerance by sending data from the last acknowledged byte without starting the entire transfer from the beginning. The data transport service also provides for the low-level access and connections between hosts for file transfer.Allcock, Bill; Foster,Ian; Nefedova, Veronika; Chervenak, Ann; Deelman, Ewa; Kesselman, Carl. High-performance remote access to climate simulation data: A challenge problem for data grid technologies.
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Bootstrap percolation is a random process studied as an epidemic model and as a model for fault tolerance for distributed computing. It consists of selecting a random subset of active cells from a lattice or other space, and then considering the -core of the induced subgraph of this subset. In k-core or bootstrap percolation on weakly interconnected networks, the interconnections can be regarded as an external field at the transition.
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Intel now aimed to build a sophisticated complete system in a few LSI chips, that was functionally equal to or better than the best 32-bit minicomputers and mainframes requiring entire cabinets of older chips. This system would support multiprocessors, modular expansion, fault tolerance, advanced operating systems, advanced programming languages, very large applications, ultra reliability, and ultra security. Its architecture would address the needs of Intel's customers for a decade.
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Sexual reproduction derives from recombination, where parent genotypes are reorganized and shared with the offspring. This stands in contrast to single-parent asexual replication, where the offspring is always identical to the parents (barring mutation). Recombination supplies two fault-tolerance mechanisms at the molecular level: recombinational DNA repair (promoted during meiosis because homologous chromosomes pair at that time) and complementation (also known as heterosis, hybrid vigor or masking of mutations).
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High availability and recovery features enable transparent recovery in conjunction with failover servers. Since Lustre 2.10 the LNet Multi-Rail (MR) feature allows link aggregation of two or more network interfaces between a client and server to improve bandwidth. The LNet interface types do not need to be the same network type. In 2.12 Multi-Rail was enhanced to improve fault tolerance if multiple network interfaces are available between peers.
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In 1976, Hamilton co-founded with Saydean Zeldin a company called Higher Order Software (HOS) to further develop ideas about error prevention and fault tolerance emerging from their experience at MIT working on the Apollo program. They created a product called USE.IT, based on the HOS methodology they developed at MIT.M. Hamilton, S. Zeldin (1976) "Higher order software—A methodology for defining software" IEEE Transactions on Software Engineering, vol.
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Reliability improvements target all aspects of UAV systems, using resilience engineering and fault tolerance techniques. Individual reliability covers robustness of flight controllers, to ensure safety without excessive redundancy to minimize cost and weight. Besides, dynamic assessment of flight envelope allows damage-resilient UAVs, using non-linear analysis with ad hoc designed loops or neural networks. UAV software liability is bending toward the design and certifications of crewed avionics software.
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Balazinska was born in Poland. Her family moved to Algeria, where she studied in a Polish and French speaking school, and then to Quebec, Canada, where she did her university studies in computer engineering at the Polytechnique Montréal. She completed her Ph.D. in computer science in 2005 at the Massachusetts Institute of Technology. Her dissertation, Fault-Tolerance and Load Management in a Distributed Stream Processing System, was supervised by Hari Balakrishnan.
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Based on the benefit from the DHR structure in functionally equivalence, Mimic Defense keeps the fault tolerance and intrusion tolerance property in MDB as long as consistent mistakes arise by falling from the majority of executive entities at the same time. MTD emphasizes the functional recovery after the compromise, which is called resilience and tenacity. Obviously, the protective effect of the former is much higher than that of the latter.
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The adoption of this distinction in a computer architecture, usually means that protection is provided as a fault tolerance mechanism by hardware/firmware and kernel, whereas the operating system and applications implement their security policies. In this design, security policies rely therefore on the protection mechanisms and on additional cryptography techniques. The major hardware approachSwift 2005 p.26 for security or protection is the use of hierarchical protection domains.
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Fault tolerance in the Tricon is achieved by means of a Triple- Modular Redundant (TMR) architecture. The Tricon provides error-free, uninterrupted control in the presence of either hard failures of components, or transient faults from internal or external sources. The Tricon is designed with a fully triplicated architecture throughout, from the input modules through the Main Processors to the output modules. Every I/O module houses the circuitry for three independent legs.
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Superstabilization is a concept of fault-tolerance in distributed computing. Superstabilizing distributed algorithms combine the features of self- stabilizing algorithms and dynamic algorithms. A superstabilizing algorithm – just like any other self-stabilizing algorithm – can be started in an arbitrary state, and it will eventually converge to a legitimate state. Additionally, a superstabilizing algorithm will recover rapidly from a single change in the network topology (adding or removing one edge or node in the network).
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The relational data model became popular after its publication by Edgar F. Codd in 1970. Due to increasing requirements for horizontal scalability and fault tolerance, NoSQL databases became prominent after 2009. NoSQL databases use a variety of data models, with document, graph, and key- value models being popular.Infoworld, "The Rise of the Multi-Model Database" A Multi-model database is a database that can store, index and query data in more than one model.
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Brian Randell's main research interests are in the field of computer science, specifically on system dependability and fault tolerance. His interest in the history of computing was started by coming across the then almost unknown work of Percy Ludgate. This was over thirty years ago, when he was preparing an inaugural lecture, and led to his producing the book: "The Origins of Computers". This triggered his further investigation of the Colossus wartime code-breaking machines.
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Versant does synchronous pair replication. Full replication for fault tolerance only requires installation of one configuration file specifying the buddy node names: New connections notice the existence of the replica file and on connect, check the file for a buddy pair and if it exists, connect to both buddies. This could be a distributed database so that there are many buddy pairs. Then all transactional changes are committed synchronously to the buddy database server processes.
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By default AD assigns all operations master roles to the first DC created in a forest. To provide fault tolerance, there should be multiple domain controllers available within each domain of the Forest. If new domains are created in the forest, the first DC in a new domain holds all of the domain-wide FSMO roles. This is not a satisfactory position if the domain has a large number of domain controllers.
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It is possible to mitigate this by guarding the elements against locking or by limiting the force exerted by a single element. But these measures reduce both the effectiveness of the system and introduce new points of failure. The analysis of the serial configuration shows that it remains operational when one element is locked-up. This fact is important for the High Redundancy Actuator, as fault tolerance is required for different fault types.
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Modern communications theory has introduced methods to increase fault tolerance in cell organizations. Game theory and graph theory have been applied to the study of optimal covert network design.Lindelauf, R.H.A. et al. 2009. "The influence of secrecy on the communication structure of covert networks" Social Networks 31: 126 In the past, if cell members only knew the cell leader, and the leader was neutralized, the cell was cut off from the rest of the organization.
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Many RAID levels employ an error protection scheme called "parity", a widely used method in information technology to provide fault tolerance in a given set of data. Most use simple XOR, but RAID 6 uses two separate parities based respectively on addition and multiplication in a particular Galois field or Reed–Solomon error correction.Dawkins, Bill and Jones, Arnold. "Common RAID Disk Data Format Specification" [Storage Networking Industry Association] Colorado Springs, 28 July 2006.
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Even though the use of data lineage approaches is a novel way of debugging of big data pipelines, the process is not simple. The challenges include scalability of the lineage store, fault tolerance of the lineage store, accurate capture of lineage for black box operators and many others. These challenges must be considered carefully and trade offs between them need to be evaluated to make a realistic design for data lineage capture.
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Distributed software is often structured in terms of clients and services. Each service comprises one or more servers and exports operations that clients invoke by making requests. Although using a single, centralized server is the simplest way to implement a service, the resulting service can only be as fault tolerant as the processor executing that server. If this level of fault tolerance is unacceptable, then multiple servers that fail independently must be used.
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He worked on the Hard Real-time operating system, Maruti, which also addressed the fault tolerance issues. This work led to the two books he wrote in these areas. Agrawala started the MIND Lab (Maryland Information and Network Dynamics Lab) in 2001 and continues to serve as its director. The Lab has been involved in the development indoor location technology and accurate clock synchronization technology, and actively participated in the semantic web research.
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Self-stabilization is a concept of fault- tolerance in distributed computing. A distributed system that is self- stabilizing will end up in a correct state no matter what state it is initialized with. That correct state is reached after a finite number of execution steps. Many years after the seminal paper of Edsger Dijkstra in 1974, this concept remains important as it presents an important foundation for self-managing computer systems and fault-tolerant systems.
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ProActive Parallel Suite is an open-source software for enterprise workload orchestration, part of the OW2 community. A workflow model allows to define the set of executables and scripts written in any scripting language along with their dependencies, so ProActive Parallel Suite can schedule and orchestrate executions while optimising the use of computational resources. ProActive Parallel Suite is based on the "active object"-based Java framework to optimise task distribution and fault-tolerance.
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In most of these protocols, an address (whether it is initiator or target) is roughly equivalent to physical device's port. Situations where a single physical port hosts multiple addresses, or where a single address is accessible from one device's multiple ports are not very common, . Even when using multipath I/O to achieve fault tolerance, the device driver switches between different targets or initiators statically bound on physical ports, instead of sharing a static address between physical ports.
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Robinson leads the Security And Fault Tolerance (SAF-T) Research group at Vanderbilt University. In particular, his work focuses on the design and implementation of computing systems for industrial and medical applications. In these systems, Robinson makes use of information leakage to bridge the fields of computer networking and architecture. In 2010 Robinson was the first African-American to earn tenure in the department of engineering, and in 2018 became the first African-American to achieve tenure.
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Error-handling refers to the programming practice of anticipating and coding for error conditions that may arise when the program runs. Exception-handling is a programming-language construct or hardware mechanism designed to handle the occurrence of exceptions, special conditions that change the normal flow of program execution. Fault tolerance is a collection of techniques that increase software reliability by detecting errors and then recovering from them if possible or containing their effects if recovery is not possible.
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Cassandra is designed as a distributed system, for deployment of large numbers of nodes across multiple data centers. Key features of Cassandra’s distributed architecture are specifically tailored for multiple- data center deployment, for redundancy, for failover and disaster recovery. ; Scalability : Designed to have read and write throughput both increase linearly as new machines are added, with the aim of no downtime or interruption to applications. ; Fault-tolerant : Data is automatically replicated to multiple nodes for fault-tolerance.
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16 Fault tolerance can be achieved in a data grid by providing mechanisms that ensures data transfer will resume after each interruption until all requested data is received.Venugopal, Srikumar; Buyya, Rajkumar; Ramamohanarao, Kotagiri. A taxonomy of data grids for distributed data sharing - management and processing p.21 There are multiple possible methods that might be used to include starting the entire transmission over from the beginning of the data to resuming from where the transfer was interrupted.
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Mangle enables you to run chaos engineering experiments seamlessly against applications and infrastructure components to assess resiliency and fault tolerance. It is designed to introduce faults with very little pre- configuration and can support any infrastructure that you might have including K8S, Docker, vCenter or any Remote Machine with ssh enabled. With its powerful plugin model, you can define a custom fault of your choice based on a template and run it without building your code from scratch.
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Current staffing consists of a core of technicians who perform routine maintenance and repair equipment failures. For fault tolerance and backup, CFB Esquimalt can operate the receiver and transmitter sites at NRS Mill Cove and NRS Newport Corner (in Nova Scotia) respectively. CFB Halifax can also operate the receivers and transmitters at Aldergrove and Matsqui. Between 1996 and 2006, several buildings on the station were dismantled, including the single quarters, the station's water tower, and the junior ranks mess.
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A VOIP solution is included, although it can integrate with a pre-existing voice solution. Fault tolerance for low bandwidth, high latency, and/or error- prone TCP/IP networks is supported by CPOF's multi-tiered client-server architecture. It can thus be deployed on systems from a two-hop geosynchronous satellite link to a radio network such as JNN while remaining collaborative. The software is largely Java-based, but is only currently deployed on a Microsoft Windows platform.
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Riak (pronounced "ree-ack" ) is a distributed NoSQL key-value data store that offers high availability, fault tolerance, operational simplicity, and scalability. In addition to the open-source version, it comes in a supported enterprise version and a cloud storage version. Riak implements the principles from Amazon's Dynamo paper with heavy influence from the CAP Theorem. Written in Erlang, Riak has fault tolerant data replication and automatic data distribution across the cluster for performance and resilience.
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IP fragmentation attacks exploit this process as an attack vector. Part of the TCP/IP suite is the Internet Protocol (IP) which resides at the Internet Layer of this model. IP is responsible for the transmission of packets between network end points. IP includes some features which provide basic measures of fault-tolerance (time to live, checksum), traffic prioritization (type of service) and support for the fragmentation of larger packets into multiple smaller packets (ID field, fragment offset).
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In Ethereum all smart contracts are stored publicly on every node of the blockchain, which has costs. Being a blockchain means it is secure by design and is an example of a distributed computing system with high Byzantine fault tolerance. The downside is that performance issues arise in that every node is calculating all the smart contracts in real time, resulting in lower speeds. As of January 2016, the Ethereum protocol could process about 25 transactions per second.
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Operational databases are increasingly supporting distributed database architecture that can leverage distribution to provide high availability and fault tolerance through replication and scale out ability. The growing role of operational databases in the IT industry is moving fast from legacy databases to real-time operational databases capable to handle distributed web and mobile demand and to address Big data challenges. Recognizing this, Gartner started to publish the Magic Quadrant for Operational Database Management Systems in October 2013.
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Standalone DFS allows for only DFS roots on the local computer, and thus does not use Active Directory. Domain-based DFS roots exist within Active Directory and can have their information distributed to other domain controllers within the domain – this provides fault tolerance to DFS. DFS roots that exist on a domain must be hosted on a domain controller or on a domain member server. The file and root information is replicated via the Microsoft File Replication Service (FRS).
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The transmission system provides for base load and peak load capability, with safety and fault tolerance margins. The peak load times vary by region largely due to the industry mix. In very hot and very cold climates home air conditioning and heating loads have an effect on the overall load. They are typically highest in the late afternoon in the hottest part of the year and in mid-mornings and mid-evenings in the coldest part of the year.
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In recent years, HIL for power systems has been used for verifying the stability, operation, and fault tolerance of large-scale electrical grids. Current-generation real-time processing platforms have the capability to model large-scale power systems in real-time. This includes systems with more than 10,000 buses with associated generators, loads, power- factor correction devices, and network interconnections. These types of simulation platforms enable the evaluation and testing of large-scale power systems in a realistic emulated environment.
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The latter may fail, and without backup, the system risks failure. The reliability and availability of system is improved through application of multiple redundant agents. Fault tolerance relates to the structure of a collaborative e-Work system. The combination of the FTT and CEDP principles extend into resilience by teaming frameworks that enable the formation, re- configuration, and operation of e-Work systems via “disruption-prone agents” that achieve higher resilience than an equivalent system of “flaw-less/more reliable” agents.
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Two systems were designed, the BiiN 20 was an entry-level machine with one or two processors, and an interesting battery-backed disk-cache. The larger BiiN 60 was similar, but supported up to eight CPUs. Both machines could be used in larger multi- machine systems. One interesting feature of the BiiN was that the CPU sets could be used to provide either fault tolerance, as in the Tandem systems, or parallel processing, as in the Pyramid and Sequent systems.
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Through independently operating servers, cross-certification can provide third-party proof of the validity of a time interval chain and irrefutable evidence of consensus on the current time. Transient-key cryptographic systems display high Byzantine fault tolerance. A web of interconnected cross-certifying servers in a distributed environment creates a widely witnessed chain of trust that is as strong as its strongest link. By contrast, entire hierarchies of traditional public key systems can be compromised if a single private key is exposed.
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In addition to SRI and UCLA, University of California, Santa Barbara and the University of Utah were part of the original four network nodes. By December 5, 1969, the entire four-node network was connected. In the 1970s, SRI developed packet-switched radio (a precursor to wireless networking), over-the-horizon radar, Deafnet, vacuum microelectronics, and software-implemented fault tolerance. The first true Internet transmission occurred on November 22, 1977, when SRI originated the first connection between three disparate networks.
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Privilege rings for the x86 available in protected mode In computer science, hierarchical protection domains, often called protection rings, are mechanisms to protect data and functionality from faults (by improving fault tolerance) and malicious behavior (by providing computer security). This approach is diametrically opposite to that of capability-based security. Computer operating systems provide different levels of access to resources. A protection ring is one of two or more hierarchical levels or layers of privilege within the architecture of a computer system.
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Each switch and router are connected by two cables. By having more than one cable connecting each device, it ensures network connectivity to any area of the enterprise-wide network. Parallel backbones are more expensive than other backbone networks because they require more cabling than the other network topologies. Although this can be a major factor when deciding which enterprise-wide topology to use, the expense of it makes up for the efficiency it creates by adding increased performance and fault tolerance.
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A Westlock system is divided into a number of components, called the Central Interlocking Processor (CIP), Trackside Interface (TIF) and Technicians Workstation (TW). The hardware used by the TIF and CIP is similar, based around a 2-out-of-3 architecture, whereby all safety-critical functions are performed in three separate processing lanes and the results voted upon. This provides some fault tolerance whereby a single module can fail and the system can continue operating in 2-out-of-2 mode.
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Robert Eliot Shostak is an American computer scientist and Silicon Valley entrepreneur. He is most noted academically for his seminal work in the branch of distributed computing known as Byzantine Fault Tolerance. He is also known for co-authoring the Paradox Database, and most recently, the founding of Vocera Communications, a company that makes wearable, Star Trek-like communication badges. Shostak has authored more than forty academic papers and patents, and was editor of the 7th Conference on Automated Deduction.
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Such transfers deliver huge volumes of data from one datacenter to multiple datacenters for various applications: search engines distribute search index updates periodically (e.g. every 24 hours), social media applications push new content to many cache locations across the world (e.g. YouTube and Facebook), and backup services make several geographically dispersed copies for increased fault tolerance. To maximize bandwidth utilization and reduce completion times of bulk transfers, a variety of techniques have been proposed for selection of multicast forwarding trees.
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Tandem Computers was founded in 1974 by James (Jimmy) Treybig. Treybig first saw the market need for fault tolerance in OLTP (online transaction processing) systems while running a marketing team for Hewlett Packard's HP 3000 computer division, but HP was not interested in developing for this niche. He then joined the venture capital firm Kleiner & Perkins and developed the Tandem business plan there."Tandem History: An Introduction". Center magazine, vol 6 number 1, Winter 1986, a magazine for Tandem employees.
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Database transactions can be used to introduce some level of fault tolerance and data integrity after recovery from a crash. A database transaction is a unit of work, typically encapsulating a number of operations over a database (e.g., reading a database object, writing, acquiring lock, etc.), an abstraction supported in database and also other systems. Each transaction has well defined boundaries in terms of which program/code executions are included in that transaction (determined by the transaction's programmer via special transaction commands).
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In the current situation, the application of distributed systems is commonly used. Using erasure code to store data in the bottom of the distributed storage system can increase the fault tolerance of the system. At the same time, compared to the traditional replica strategy, erasure code technology can exponentially improve the reliability of the system for the same redundancy. BRS encoding can be applied to distributed storage systems, for example, BRS encoding can be used as the underlying data encoding while using HDFS.
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Signal aspects are designed to incorporate some degree of fault tolerance. Aspects are often designed so that a faulty or obscured lamp will cause the resulting aspect to be more restrictive than the intended one. Operating rules (GCOR, NORAC or CROR) require that dark or obscured signal heads be treated as displaying their most restrictive aspect (i.e. stop), but fault-tolerant aspect design can help the engineer take a safer course of action before the failure of a signal becomes apparent.
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A number of researchers published articles on the replicated state machine approach in the early 1980s. Anita Borg described an implementation of a fault tolerant operating system based on replicated state machines in a 1983 paper "A message system supporting fault tolerance". Leslie Lamport also proposed the state machine approach, in his 1984 paper on "Using Time Instead of Timeout In Distributed Systems". Fred Schneider later elaborated the approach in his paper "Implementing Fault-Tolerant Services Using the State Machine Approach: A Tutorial".
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Secure Scuttlebutt (SSB) is a peer-to peer communication protocol, mesh network, and self-hosted social media ecosystem. Each user hosts their own content and the content of the peers they follow, which provides fault tolerance and eventual consistency. Messages are digitally signed and added to an append-only list of messages published by an author. SSB is primarily used for implementing distributed social networks, and utilizes cryptography to assure that content remains unforged as it is propagated through the network.
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Bypass switches and TAPs add acquisition cost to the monitoring solution, although they may save cost in the long run by increasing network uptime. Bypass switches move the single point of failure from the in-line monitoring appliance to the bypass switch itself. This should be a net gain in reliability, because the bypass switch is a simpler device than the monitoring appliance, and because it is designed for fault-tolerance. Nevertheless, reliability is an important criterion when evaluating bypass switch solutions.
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Third Edition. San Francisco: Sybex The transmission medium layout used to link devices is the physical topology of the network. For conductive or fiber optical mediums, this refers to the layout of cabling, the locations of nodes, and the links between the nodes and the cabling. The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunication circuits.
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This makes access to grid resources dynamic and conditional upon local constraints. Centralized management techniques for these resources are limited in their scalability both in terms of execution efficiency and fault tolerance. Provision of services across such platforms requires a distributed resource management mechanism and the peer-to-peer clustered GOS appliances allow a single storage image to continue to expand, even if a single GOS appliance reaches its capacity limitations. The cluster shares a common, aggregate presentation of the data stored on all participating GOS appliances.
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Violin does not use solid state drives (SSD), but instead uses a proprietary design referred to as flash fabric architecture (FFA). The FFA technology consists of: a mesh of NAND flash dies, modules that organize the mesh of flash dies, and a proprietary switched architecture for fault tolerance. In September 2011, Violin announced the 6000 series all-silicon shared flash memory storage arrays. vMOS is Violin Memory's software layer that integrates with the FFA to provide data protection, management and connectivity to the host.
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Worst case is when the process starting the election is the immediate following to the one with greatest UID: it takes N-1 messages for the election message to reach it, then N messages for it to get back its own UID, then other N messages to send everyone in the ring the elected message. This algorithm is not very fault tolerant. Fault tolerance can be increased If every process knows the whole topology, by introducing ACK messages and skipping faulty nodes on sending messages.
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In skip graphs, fault tolerance describes the number of nodes which can be disconnected from the skip graph by failures of other nodes. Two failure models have been examined; random failures and adversarial failures. In the random failure model any node may fail independently from any other node with some probability. The adversarial model assumes node failures are planned such that the worst possible failure is achieved at each step, the entire skip graph structure is known and failures are chosen to maximize node disconnection.
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Nuix markets eDiscovery, digital investigation, security & intelligence and information governance solutions based on the Nuix Engine. The Nuix Engine combines load balancing, fault tolerance and processing technologies to provide insights from large volumes of unstructured, semi-structured and structured data. Several features of the Nuix Engine were granted a patent in 2011. In November 2016, Nuix announced a new analysis platform called Nuix Insight Analytics & Intelligence and an endpoint security product, Nuix Insight Adaptive Security, that integrates cybersecurity threat prevention, detection, response, remediation, and deception.
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Additional savings can be seen from reduced need for floor space, power, cooling, networking hardware, and the other infrastructure needed to support a data center. IBM mainframes allow transparent use of redundant processor execution steps and integrity checking, which is important for critical applications in certain industries such as banking. Mainframes typically allow hot-swapping of hardware, such as processors and memory. IBM Z provides fault tolerance for all key components, including processors, memory, I/O Interconnect, power supply, channel paths, network cards, and others.
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Web Cache Communication Protocol (WCCP) is a Cisco-developed content-routing protocol that provides a mechanism to redirect traffic flows in real-time. It has built-in load balancing, scaling, fault tolerance, and service-assurance (failsafe) mechanisms. Cisco IOS Release 12.1 and later releases allow the use of either Version 1 (WCCPv1) or Version 2 (WCCPv2) of the protocol. WCCP allows utilization of Cisco Cache Engines (or other caches running WCCP) to localize web traffic patterns in the network, enabling content requests to be fulfilled locally.
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The AFCS allows the operation of a four-axis (pitch, roll, yaw and collective) autopilot and the automatic stabilisation system, and is linked in with the aircraft's flight management systems.Moir and Seabridge 2008, pp. 343–345. The AFCS, manufactured by Smiths Aerospace, is a dual-duplex system using two flight computers to provide redundancy and fault-tolerance. The AW101's navigation system includes a GPS receiver and inertial navigation system, VHF omnidirectional radio range (VOR), instrument landing system (ILS), TACAN, and automatic direction finding.
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So what > that means is, no downtime. In other words, you have got to really have > bulletproof, bombproof applications and hardware systems. So you know, what > do you use? Well one thing you have high-availability clusters or you have > the more expensive and more complex fault-tolerance servers.” Telecommunications: High Availability Software is an essential component of telecommunications equipment since a network outage can result in significant loss in revenue for telecom providers and telephone access to emergency services is an important public safety issue.
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An Internet exchange point (IX or IXP) is the physical infrastructure through which Internet service providers (ISPs) and content delivery networks (CDNs) exchange Internet traffic between their networks (autonomous systems). IXPs reduce the portion of an ISP's traffic that must be delivered via their upstream transit providers, thereby reducing the average per-bit delivery cost of their service. Furthermore, the increased number of paths available through the IXP improves routing efficiency and fault-tolerance. In addition, IXPs exhibit the characteristics of what economists call the network effect.
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Heterogeneous clusters are fully supported, and there are several deployment options that are available, including some that provide very high levels of data redundancy and fault tolerance. This feature is marketed by IBM as Informix Flexible Grid. Informix is offered in a number of editions, including free developer editions, editions for small and mid-sized business, and editions supporting the complete feature set and designed to be used in support of the largest enterprise applications. There is also an advanced data warehouse edition of Informix.
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Once recorded, the data in any given block cannot be altered retroactively without alteration of all subsequent blocks, which requires consensus of the network majority. Although blockchain records are not unalterable, blockchains may be considered secure by design and exemplify a distributed computing system with high Byzantine fault tolerance. Decentralized consensus has therefore been claimed with a blockchain. Blockchain was invented by a person (or group of people) using the name Satoshi Nakamoto in 2008 to serve as the public transaction ledger of the cryptocurrency bitcoin.
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Early cache designs focused entirely on the direct cost of cache and RAM and average execution speed. More recent cache designs also consider energy efficiency, fault tolerance, and other goals. Researchers have also explored use of emerging memory technologies such as eDRAM (embedded DRAM) and NVRAM (non-volatile RAM) for designing caches. There are several tools available to computer architects to help explore tradeoffs between the cache cycle time, energy, and area; the CACTI cache simulator and the SimpleScalar instruction set simulator are two open-source options.
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Fault-tolerance is gained, but the identical backup system doubles the costs. For this reason, starting , the distributed systems research community began to explore alternative methods of replicating data. An outgrowth of this work was the emergence of schemes in which a group of replicas could cooperate, with each process acting as a backup while also handling a share of the workload. Computer scientist Jim Gray analyzed multi- primary replication schemes under the transactional model and published a widely cited paper skeptical of the approach "The Dangers of Replication and a Solution".
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Clients may be tracked by IP address, DNS name, software version they use, files they share, queries they initiate, and queries they answer to. Much is known about the network structure, routing schemes, performance load and fault tolerance of P2P systems in general and Gnutella in particular. This document concentrates on the user privacy that reveals by the Gnutella and eMule networks. It might be surprising, but the eMule protocol does not provide much privacy to the users, although it is a P2P protocol which is supposed to be decentralized.
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The Configurable Fault Tolerant Processor Project aims to demonstrate the feasibility of using Field Programmable Gate Arrays (FPGAs) for spacecraft computer processing by applying various fault tolerance techniques to the designs. CFTP provides a valuable testbed for on-orbit evaluation of various fault tolerant concepts. The use of FPGAs provides added flexibility, allowing on-orbit upgrades and rapid development cycles. Using Commercial off the shelf (COTS) technology allows the engineer to produce more technologically advanced designs at a lower cost and in a shorter time than using more traditional space-grade components.
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A parity drive is a hard drive used in a RAID array to provide fault tolerance. For example, RAID 3 uses a parity drive to create a system that is both fault tolerant and, because of data striping, fast.Definitions of RAID configurations Retrieved on 2010-11-15 Basically, a single data bit is added to the end of a data block to ensure the number of bits in the message is either odd or even. One way to implement a parity drive in a RAID array is to use the exclusive or, or XOR, function.
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Distributed applications that run across datacenters usually replicate data for the purpose of synchronization, fault resiliency, load balancing and getting data closer to users (which reduces latency to users and increases their perceived throughput). Also, many applications, such as Hadoop, replicate data within a datacenter across multiple racks to increase fault tolerance and make data recovery easier. All of these operations require data delivery from one machine or datacenter to multiple machines or datacenters. The process of reliably delivering data from one machine to multiple machines is referred to as Reliable Group Data Delivery (RGDD).
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The goals have been to detect and tolerate one error in any register without software intervention, and to suppress effects from Single Event Transient (SET) errors in combinational logic. The LEON family includes the first LEON1 VHSIC Hardware Description Language (VHDL) design that was used in the LEONExpress test chip developed in 0.25 μm technology to prove the fault-tolerance concept. The second LEON2 VHDL design was used in the processor device AT697 from Atmel (F) and various system-on- chip devices. These two LEON implementations were developed by ESA.
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The original formulation is from Jerome Saltzer: Peter J. Denning, in his paper "Fault Tolerant Operating Systems", set it in a broader perspective among four fundamental principles of fault tolerance. Dynamic assignments of privileges was earlier discussed by Roger Needham in 1972. Historically, the oldest instance of least privilege is probably the source code of login.c, which begins execution with super-user permissions and—the instant they are no longer necessary—dismisses them via setuid() with a non-zero argument as demonstrated in the Version 6 Unix source code.
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The IP network multipathing or IPMP is a facility provided by Solaris to provide fault-tolerance and load spreading for network interface cards (NICs). With IPMP, two or more NICs are dedicated for each network to which the host connects. Each interface can be assigned a static "test" IP address, which is used to assess the operational state of the interface. Each virtual IP address is assigned to an interface, though there may be more interfaces than virtual IP addresses, some of the interfaces being purely for standby purposes.
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FlexRay is an automotive network communications protocol developed by the FlexRay Consortium to govern on-board automotive computing. It is designed to be faster and more reliable than CAN and TTP, but it is also more expensive. The FlexRay consortium disbanded in 2009, but the FlexRay standard is now a set of ISO standards, ISO 17458-1 to 17458-5. FlexRay is a communication bus designed to ensure high data rates, fault tolerance, operating on a time cycle, split into static and dynamic segments for event-triggered and time- triggered communications.
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FlexRay supports data rates up to , explicitly supports both star and "party line" bus topologies, and can have two independent data channels for fault-tolerance (communication can continue with reduced bandwidth if one channel is inoperative). The bus operates on a time cycle, divided into two parts: the static segment and the dynamic segment. The static segment is preallocated into slices for individual communication types, providing stronger determinism than its predecessor CAN. The dynamic segment operates more like CAN, with nodes taking control of the bus as available, allowing event-triggered behavior.
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Another security mechanism is that code files can only be created by trusted compilers. Malicious programmers cannot create a program and call it a compiler – a program could only be converted to be a compiler by an operator with sufficient privileges with the 'mc' make compiler operator command. The MCP implements a Journaling file system, providing fault tolerance in case of disk failure, loss of power, etc. It is not possible to corrupt the file system (except by the operating system or other trusted system software with direct access to its lower layers) .
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Byzantine failures are considered the most general and most difficult class of failures among the failure modes. The so-called fail- stop failure mode occupies the simplest end of the spectrum. Whereas fail-stop failure mode simply means that the only way to fail is a node crash, detected by other nodes, Byzantine failures imply no restrictions, which means that the failed node can generate arbitrary data, including data that makes it appear like a functioning node. Thus, Byzantine failures can confuse failure detection systems, which makes fault tolerance difficult.
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DreamHost's DreamObjects is a cloud storage service powered by Ceph. Ceph's distributed object storage system allows for storing DreamObjects’ data on multiple disks across multiple servers for high fault-tolerance. DreamObjects users store any kind of data (developer content, video, music, etc.) and make it accessible from anywhere in the cloud. Because data is redundantly stored across multiple locations, a fault in any part of the redundant system – such as the loss of a server – will go unnoticed by users, as a user's data remains available and accessible.
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Chandra Kintala (1948–2009) was a computer science researcher in New Jersey, United States and Bangalore, India from 2006–2009. He worked at Bell Labs in AT&T;, Lucent and Avaya in New Jersey, where he and Dr. David Belanger invented a language and a software tool used in AT&T; for data analytics on very large databases. With Dr. Yennun Huang, he worked on Software-implemented Fault Tolerance and Software Rejuvenation in the 1990s. He also worked in distributed systems and network software research at Bell Labs.
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Perhaps Shostak's most notable academic contribution is to have originated the branch of distributed computing known as Byzantine fault tolerance, also called interactive consistency. This work was also conducted in connection with the SIFT project at SRI. SIFT was conceived by John H. Wensley, who proposed using a network of general-purpose computers to reliably control an aircraft even if some of those computers were faulty. The computers would exchange messages as to the current time and state of the aircraft (each would have its own sensors and clock), and would thereby reach a consensus.
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Basho was the developer of Riak, an open source distributed database that offers high availability, fault tolerance, operation simplicity and scalability. Riak Enterprise was a commercial version of the database offered by Basho, the project's sponsor, with advanced multi-data center replication and enterprise support. Riak is a key value store system that can collect unstructured data and store it as objects in buckets that can then be queried. It's also highly scalable, able to distribute itself over a server cluster and add new servers as needed, while maintaining its own high availability.
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EtherChannel between a switch and a server. EtherChannel is a port link aggregation technology or port-channel architecture used primarily on Cisco switches. It allows grouping of several physical Ethernet links to create one logical Ethernet link for the purpose of providing fault-tolerance and high- speed links between switches, routers and servers. An EtherChannel can be created from between two and eight active Fast, Gigabit or 10-Gigabit Ethernet ports, with an additional one to eight inactive (failover) ports which become active as the other active ports fail.
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These are typically handled by whitelisting or exception lists. Also, legitimate mail might not get delivered if the retry comes from a different IP address than the original attempt. When the source of an email is a server farm or goes out through some other kind of relay service, it is likely that a server other than the original one will make the next attempt. For network fault tolerance, their IPs can belong to completely unrelated address blocks, thereby defying the simple technique of identifying the most significant part of the address.
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Advanced research and evolution are led mostly by universities active on topics like RF propagation studies, protocol optimization, fault tolerance in noisy environments, etc. The UAG brings skills from IoT laboratories to compare different behavior of radio technologies in dense urban areas. ;Outreach Working Group: Gathers end user requirements for submittal to the outreach working group and also leads all public outreach for the Alliance. The OWG is also responsible to showcase different use cases in order to help industries, cities, universities evaluate the added value of DASH7 for their context.
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The general steps of N-version programming are: # An initial specification of the intended functionality of the software is developed. The specification should unambiguously define: functions, data formats (which include comparison vectors, c-vectors, and comparison status indicators, cs-indicators), cross- check points (cc-points), comparison algorithm, and responses to the comparison algorithm.A.A. Avizienis, “The Methodology of N-version Programming” , Software Fault Tolerance, edited by M. Lyu, John Wiley & Sons, 1995. # From the specifications, two or more versions of the program are independently developed, each by a group that does not interact with the others.
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IEEE 802.1CB Frame Replication and Elimination for Reliability (FRER) sends duplicate copies of each frame over multiple disjoint paths, to provide proactive seamless redundancy for control applications that cannot tolerate packet losses. The packet replication can use traffic class and path information to minimize network congestion. Each replicated frame has a sequence identification number, used to re-order and merge frames and to discard duplicates. FRER requires centralized configuration management and needs to be used with 802.1Qcc and 802.1Qca. Industrial fault-tolerance HSR and PRP specified in IEC 62439-3 are supported.
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The aim of high redundancy actuation is not to produce man-made muscles, but to use the same principle of cooperation in technical actuator's to provide intrinsic fault tolerance. To achieve this, a high number of small actuator elements are assembled in parallel and in series to form one actuator (see Series and parallel circuits). Faults within the actuator will affect the maximum capability, but through robust control, full performance can be maintained without either adaptation or reconfiguration. Some form of condition monitoring is necessary to provide warnings to the operator calling for maintenance.
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Mootaz Elnozahy is a computer scientist. He is currently a professor of computer science and dean of the computer, electrical and mathematical science, and engineering division at King Abdullah University of Science and Technology. Elnozahy's research area is in systems, including high-performance computing, power-aware computing, fault tolerance, operating systems, system architecture, and distributed systems. His work on rollback-recovery is now a standard component of graduate courses in fault-tolerant computing, and he has made seminal contributions in checkpoint/restart, and in general on the complex hardware-software interactions in resilience.
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In general, this implies that in lossy networks the quality of a media stream is not proportional to the amount of correctly received data. Besides increased fault tolerance, MDC allows for rate-adaptive streaming: Content providers send all descriptions of a stream without paying attention to the download limitations of clients. Receivers that cannot sustain the data rate only subscribe to a subset of these streams, thus freeing the content provider from sending additional streams at lower data rates. The vast majority of state-of-the art codecs uses single description (SD) video coding.
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The company was founded by Eli Alon and Dale Shipley (both from Intel) as Tolerant Systems in 1983 to build fault-tolerant computer systems based on the idea of "shoe box" building blocks. The shoe box consisted of an OS processor, running a version of Unix called TX, and on which applications ran, and an I/O processor, running a Real Time Executive, developed by Tolerant, called RTE: both processors were 320xx processors. The system was marketed as the "Eternity Series." The TX software gained a level of fault-tolerance through check-pointing technology.
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Apache Flink includes a lightweight fault tolerance mechanism based on distributed checkpoints. A checkpoint is an automatic, asynchronous snapshot of the state of an application and the position in a source stream. In the case of a failure, a Flink program with checkpointing enabled will, upon recovery, resume processing from the last completed checkpoint, ensuring that Flink maintains exactly-once state semantics within an application. The checkpointing mechanism exposes hooks for application code to include external systems into the checkpointing mechanism as well (like opening and committing transactions with a database system).
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Round-robin DNS is a technique of load distribution, load balancing, or fault- tolerance provisioning multiple, redundant Internet Protocol service hosts, e.g., Web server, FTP servers, by managing the Domain Name System's (DNS) responses to address requests from client computers according to an appropriate statistical model. In its simplest implementation, round-robin DNS works by responding to DNS requests not only with a single potential IP address, but with a list of potential IP addresses corresponding to several servers that host identical services. The order in which IP addresses from the list are returned is the basis for the term round robin.
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Each step in the design and refinement of the system would be recorded as part of an integrated repository. In addition to the artifacts of software development the processes, the various definitions and transformations, would also be recorded in a way that they could be analyzed and also replayed later as needed. The idea was that each step would be a transformation that took into account various non-functional requirements for the implemented system. For example, requirements to use specific programming languages such as Ada or to harden code for real time mission critical fault tolerance.
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This "digitisation" method facilitates the use of a hierarchical and cell-based approach for microfluidic biochip design. Therefore, digital microfluidics offers a flexible and scalable system architecture as well as high fault-tolerance capability. Moreover, because each droplet can be controlled independently, these systems also have dynamic reconfigurability, whereby groups of unit cells in a microfluidic array can be reconfigured to change their functionality during the concurrent execution of a set of bioassays. Although droplets are manipulated in confined microfluidic channels, since the control on droplets is not independent, it should not be confused as "digital microfluidics".
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HailDB is a standalone, embeddable form of the InnoDB Storage Engine. Given that HailDB is based on the same code base as the InnoDB Storage Engine, it contains many of the same features: high-performance and scalability, multiversion concurrency control (MVCC), row-level locking, deadlock detection, fault tolerance, automatic crash recovery, etc. However, because the embedded engine is completely independent from MySQL, it lacks server components such as networking, object-level permissions, etc. By eliminating the MySQL server overhead, InnoDB has a small footprint and is well-suited for embedding in applications which require high-performance and concurrency.
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Ultra Enterprise 4000, rear In 1996, Sun replaced the SPARCserver 1000E and SPARCcenter 2000E models with the Ultra Enterprise 3000, 4000, 5000 and 6000 servers. These are multiprocessor servers based on a common hardware architecture incorporating the Gigaplane packet-switched processor/memory bus and UltraSPARC-I or II processors. High availability and fault-tolerance features are included in the X000 systems which are intended for mission- critical applications. The 3000 model is a deskside server configurable with up to six processors and 10 internal disks, while the 4000 is a rack-mount system with up to 14 processors.
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Randell was employed at English Electric from 1957 to 1964 where he was working on compilers. His work on ALGOL 60 is particularly well known, including the development of the compiler for the English Electric KDF9, an early stack machine. In 1964, he joined IBM, where he worked at the Thomas J. Watson Research Center on high performance computer architectures and also on operating system design methodology. In May 1969, he became a Professor of Computing Science at the then named University of Newcastle upon Tyne, where he has worked since then in the area of software fault tolerance and dependability.
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Michael R. Lyu, Ph.D., is a software engineer. He is now a professor at the Chinese University of Hong Kong in Shatin, Hong Kong. Michael is well known to the software engineering community as the editor of two classic book volumes in software reliability engineering: Software Fault ToleranceMichael R. Lyu (ed.), Software Fault Tolerance, Wiley, 1995 and the Handbook of Software Reliability Engineering.Michael R. Lyu (ed.), Handbook of Software Reliability Engineering, IEEE and McGraw-Hill, 1996 Both books have also been translated into Chinese and published in China.軟件可靠性工程手冊.
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The goal of WARFT is to unravel the connectivity of the human brain regions through the MMINi-DASS project. Biologically accurate brain simulations require massive computational power and thus another research initiative at WARFT is the MIP Project directed towards evolving a design method for the development of a tera-operations supercomputing cluster. Undergraduate research trainees at WARFT engage themselves in the areas of neuroscience, supercomputing architectures, processor design towards deep sub- micrometre, power-aware computing, low power issues, mixed signal design, fault tolerance and testing, digital signal processing. WARFT conducts Dhi Yantra, a workshop on brain modeling and supercomputing every year.
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In 1999, Miguel Castro and Barbara Liskov introduced the "Practical Byzantine Fault Tolerance" (PBFT) algorithm, which provides high-performance Byzantine state machine replication, processing thousands of requests per second with sub-millisecond increases in latency. After PBFT, several BFT protocols were introduced to improve its robustness and performance. For instance, Q/U, HQ, Zyzzyva, and ABsTRACTs, addressed the performance and cost issues; whereas other protocols, like Aardvark and RBFT, addressed its robustness issues. Furthermore, Adapt tried to make use of existing BFT protocols, through switching between them in an adaptive way, to improve system robustness and performance as the underlying conditions change.
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Svoboda left the unstable situation in Czechoslovakia in 1964, traveling first to Yugoslavia and from there to Greece, and then to the USA once more. Upon his arrival immigration officials were unmoved by his situation until he produced the medal given to him by the US Navy. Communication with certain authorities established his bona fides as a useful scientist, and he was quickly admitted to the country. He worked at the University of California in Los Angeles as a professor of computer sciences, refining his theories on computer design, fault tolerance, mathematics and electrical engineering, and retired in 1977.
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Bar-Ilan did important work early in her career in the fault tolerance of distributed computing, and her dissertation research was in cryptography. However, she is best known for her research on informetrics, scientometrics, information retrieval, and web search engines. Her interest in these topics stemmed from her work in the early 1990s on applications of distributed computing in library science. This work led her to perform important studies in the late 1990s on the accuracy, reliability, and stability over time of search engine results, and on the ability of search engines to handle non-English queries.
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The security of IOTA's consensus mechanism against double-spending attacks is unclear, as long as the network is immature. Essentially, in the IoT, with heterogeneous devices having varying levels of low computational power, sufficiently strong computational resources will render the tangle insecure. This is a problem in traditional proof-of-work blockchains as well, however, they provide a much greater degree of security through higher fault tolerance and transaction fees. At the beginning, when there is a lower number of participants and incoming transactions, a central coordinator is needed to prevent an attack on the IOTA tangle.
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NonStop OS is a message-based operating system designed for fault tolerance. It works with process pairs and ensures that backup processes on redundant CPUs take over in case of a process or CPU failure. Data integrity is maintained during those takeovers; no transactions or data are lost or corrupted. The operating system as a whole is branded NonStop OS and includes the Guardian layer, which is a low-level component of the operating system and the so-called OSS personality which runs atop this layer, which implements a Unix-like interface for other components of the OS to use.
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The Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails. As the name suggests, STP creates a spanning tree that characterizes the relationship of nodes within a network of connected layer-2 bridges, and disables those links that are not part of the spanning tree, leaving a single active path between any two network nodes.
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Some sources hold that word was coined in the nineteen-teens in Dodge Brothers automobile print advertising. But the word predates that period, with the Oxford English Dictionary finding its first use in 1901. As interest in fault tolerance and system reliability increased in the 1960s and 1970s, dependability came to be a measure of [x] as measures of reliability came to encompass additional measures like safety and integrity.Brian Randell, "Software Dependability: A Personal View", in the Proc of the 25th International Symposium on Fault-Tolerant Computing (FTCS-25), California, USA, pp 35-41, June 1995.
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The Terascale Open-source Resource and QUEue Manager (TORQUE) TORQUE resource manager, Garrick Staples, SC '06: Proceedings of the 2006 ACM/IEEE conference on Supercomputing, is a distributed resource manager providing control over batch jobs and distributed compute nodes. TORQUE can integrate with the non- commercial Maui Cluster Scheduler or the commercial Moab Workload Manager to improve overall utilization, scheduling and administration on a cluster. The TORQUE community has extended the original PBS to extend scalability, fault tolerance, and functionality. Contributors include NCSA, OSC, USC, the US DOE, Sandia, PNNL, UB, TeraGrid, and other HPC organizations.
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The more a bridge is loaded, the less likely it is to take part in the route finding process for a new destination as it will be slow to forward packets. A new AR packet will find a different route over a less busy path if one exists. This method is very different from transparent bridge usage, where redundant bridges will be inactivated; however, more overhead is introduced to find routes, and space is wasted to store them in frames. A switch with a faster backplane can be just as good for performance, if not for fault tolerance.
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Edsger Dijkstra's foundational work on concurrency, semaphores, mutual exclusion, deadlock, finding shortest paths in graphs, fault-tolerance, self- stabilization, among many other contributions comprises many of the pillars upon which the field of distributed computing is built. The Edsger W. Dijkstra Prize in Distributed Computing (sponsored jointly by the ACM Symposium on Principles of Distributed Computing and the EATCS International Symposium on Distributed Computing) is given for outstanding papers on the principles of distributed computing, whose significance and impact on the theory and/or practice of distributed computing has been evident for at least a decade.
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In this case flow processing lowers latency for individual inputs, allowing them to be completed without waiting for the entire batch to finish. However, many applications require data from all records, notably computations such as totals. In this case the entire batch must be completed before one has a usable result: partial results are not usable. Modern batch applications make use of modern batch frameworks such as Jem The Bee, Spring Batch or implementations of JSR 352 written for Java, and other frameworks for other programming languages, to provide the fault tolerance and scalability required for high-volume processing.
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After graduating from Stanford, Liskov returned to Mitre to work as research staff. Liskov has led many significant projects, including the Venus operating system, a small, low-cost and interactive timesharing system; the design and implementation of CLU; Argus, the first high-level language to support implementation of distributed programs and to demonstrate the technique of promise pipelining; and Thor, an object-oriented database system. With Jeannette Wing, she developed a particular definition of subtyping, commonly known as the Liskov substitution principle. She leads the Programming Methodology Group at MIT, with a current research focus in Byzantine fault tolerance and distributed computing.
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A logical journal stores only changes to file metadata in the journal, and trades fault tolerance for substantially better write performance.. A file system with a logical journal still recovers quickly after a crash, but may allow unjournaled file data and journaled metadata to fall out of sync with each other, causing data corruption. For example, appending to a file may involve three separate writes to: # The file's inode, to note in the file's metadata that its size has increased. # The free space map, to mark out an allocation of space for the to-be-appended data. # The newly allocated space, to actually write the appended data.
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DragonFly was a prototype test article for a propulsively landed version of the SpaceX Dragon capsule, a suborbital reusable launch vehicle (RLV), intended for low-altitude flight testing. it was planned to undergo a test program in Texas at the McGregor Rocket Test Facility, during 2014–2015. The DragonFly test vehicle is powered by eight SuperDraco engines, arranged in a redundant pattern to support fault- tolerance in the propulsion system design. SuperDracos utilize a storable propellant mixture of monomethyl hydrazine (MMH) fuel and nitrogen tetroxide oxidizer (NTO), the same propellants used in the much smaller Draco thrusters used for attitude control and maneuvering on the first-generation Dragon spacecraft.
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In quantum computing, the (quantum) threshold theorem (or quantum fault- tolerance theorem) states that a quantum computer with a physical error rate below a certain threshold can, through application of quantum error correction schemes, suppress the logical error rate to arbitrarily low levels. This shows that quantum computers can be made fault-tolerant, as an analogue to von Neumann's threshold theorem for classical computation. This result was proved (for various error models) by the groups of Aharanov and Ben-Or; Knill, Laflamme, and Zurek; and Kitaev independently. These results built off a paper of Shor, which proved a weaker version of the threshold theorem.
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Angle of attack (AOA) is a critically important flight parameter, and full-authority flight control systems, such as those equipping A330/A340 aircraft, require accurate AOA data to function properly. The aircraft was fitted with three ADIRUs to provide redundancy for fault tolerance, and the FCPCs used the three independent AOA values to check their consistency. In the usual case, when all three AOA values were valid and consistent, the average value of AOA 1 and AOA 2 was used by the FCPCs for their computations. If either AOA 1 or AOA 2 significantly deviated from the other two values, the FCPCs used a memorised value for 1.2 seconds.
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This is why CI experts work on the development of artificial neural networks based on the biological ones, which can be defined by 3 main components: the cell-body which processes the information, the axon, which is a device enabling the signal conducting, and the synapse, which controls signals. Therefore, artificial neural networks are doted of distributed information processing systems, enabling the process and the learning from experiential data. Working like human beings, fault tolerance is also one of the main assets of this principle. Concerning its applications, neural networks can be classified into five groups: data analysis and classification, associative memory, clustering generation of patterns and control.
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He is a member of the Special Interest Group on Computers, Information and Society (SIGCIS) of the Society for the History of Technology CIS, and a founding member of the Editorial Board of the IEEE Annals of the History of Computing journal. He is a Fellow of the Association for Computing Machinery (2008). He is a member of the International Federation for Information Processing (IFIP) IFIP Working Group 2.1 (WG2.1) on Algorithmic Languages and Calculi, which specified, maintains, and supports the programming languages ALGOL 60 and ALGOL 68. He is also a founding member of IFIP WG2.3 on Programming Methodology, and of IFIP WG10.4 on Dependability and Fault Tolerance.
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A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the topology of the network. The ability of routing protocols to dynamically adjust to changing conditions such as disabled data lines and computers and route data around obstructions is what gives the Internet its fault tolerance and high availability. The specific characteristics of routing protocols include the manner in which they avoid routing loops, the manner in which they select preferred routes, using information about hop costs, the time they require to reach routing convergence, their scalability, and other factors such as relay multiplexing and cloud access framework parameters.
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While hardware RAID controllers were available for a long time, they always required expensive SCSI hard drives and aimed at the server and high-end computing market. SCSI technology advantages include allowing up to 15 devices on one bus, independent data transfers, hot-swapping, much higher MTBF. Around 1997, with the introduction of ATAPI-4 (and thus the Ultra-DMA-Mode 0, which enabled fast data-transfers with less CPU utilization) the first ATA RAID controllers were introduced as PCI expansion cards. Those RAID systems made their way to the consumer market, where the users wanted the fault-tolerance of RAID without investing in expensive SCSI drives.
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The switched reluctance motor (SRM) is a form of stepper motor that uses fewer poles. The most rudimentary form of a SRM has the lowest construction cost of any electric motor because of its simple structure, and even industrial motors may have some cost reduction due to the lack of rotor windings or permanent magnets. Common uses include applications where the rotor must be held stationary for long periods, and in potentially explosive environments such as mining because it operates without a mechanical commutator. The phase windings in an SRM are electrically isolated from each other, resulting in higher fault tolerance than inverter- driven AC induction motors.
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An ortho-mode transducer is also a component commonly found on high capacity terrestrial microwave radio links. In this arrangement, two parabolic reflector dishes operate in a point to point microwave radio path (4 GHz to 85 GHz) with four radios, two mounted on each end. On each dish a T-shaped ortho-mode transducer is mounted at the rear of the feed, separating the signal from the feed into two separate radios, one operating in the horizontal polarity, and the other in the vertical polarity. This arrangement is used to increase the aggregate data throughput between two dishes on a point to point microwave path, or for fault-tolerance redundancy.
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225px In computing, MISD (multiple instruction, single data) is a type of parallel computing architecture where many functional units perform different operations on the same data. Pipeline architectures belong to this type, though a purist might say that the data is different after processing by each stage in the pipeline. Fault tolerance executing the same instructions redundantly in order to detect and mask errors, in a manner known as task replication, may be considered to belong to this type. Applications for this architecture are much less common than MIMD and SIMD, as the latter two are often more appropriate for common data parallel techniques.
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For example, a RAID 1 array has about half the total capacity as a result of data mirroring, while a RAID 5 array with drives loses of capacity (which equals to the capacity of a single drive) due to storing parity information. RAID subsystems are multiple drives that appear to be one drive or more drives to the user, but provide fault tolerance. Most RAID vendors use checksums to improve data integrity at the block level. Some vendors design systems using HDDs with sectors of 520 bytes to contain 512 bytes of user data and eight checksum bytes, or by using separate 512-byte sectors for the checksum data.
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Continuous-flow devices are adequate for many well- defined and simple biochemical applications, and for certain tasks such as chemical separation, but they are less suitable for tasks requiring a high degree of flexibility or fluid manipulations. These closed-channel systems are inherently difficult to integrate and scale because the parameters that govern flow field vary along the flow path making the fluid flow at any one location dependent on the properties of the entire system. Permanently etched microstructures also lead to limited reconfigurability and poor fault tolerance capability. Computer-aided design automation approaches for continuous-flow microfluidics have been proposed in recent years to alleviate the design effort and to solve the scalability problems.
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The use of storage systems, using modern data protection technologies has become increasingly common, particularly for larger organizations with greater capacity and performance requirements. Storage systems may be configured and attached to the PACS server in various ways, either as Direct-Attached Storage (DAS), Network-attached storage (NAS), or via a Storage Area Network (SAN). However the storage is attached, enterprise storage systems commonly utilize RAID and other technologies to provide high availability and fault tolerance to protect against failures. In the event that it is necessary to reconstruct a PACS partially or completely, some means of rapidly transferring data back to the PACS is required, preferably while the PACS continues to operate.
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ISO 26262 specifies a vocabulary (a Project Glossary) of terms, definitions, and abbreviations for application in all parts of the standard. Of particular importance is the careful definition of fault, error, and failure as these terms are key to the standard’s definitions of functional safety processes, particularly in the consideration that "A fault can manifest itself as an error ... and the error can ultimately cause a failure". A resulting malfunction that has a hazardous effect represents a loss of functional safety. Note: In contrast to other Functional Safety standards and the updated ISO 26262:2018, Fault Tolerance was not explicitly defined in ISO 26262:2011 – since it was assumed impossible to comprehend all possible faults in a system.
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The NOVA (non-volatile memory accelerated) file system is an open-source, log- structured file system for byte-addressable persistent memory (for example non-volatile dual in-line memory module (NVDIMM) and 3D XPoint DIMMs) for Linux. NOVA is designed specifically for byte-addressable persistent memories and aims to provide high-performance, atomic file and metadata operations, and fault tolerance. To meet these goals NOVA combines several techniques found in other file systems. NOVA uses log structure, copy-on-write (COW), journaling, and log-structured metadata updates to provide strong atomicity guarantees, and it uses a combination replication, metadata checksums, and RAID 4 parity to protect data and metadata from media errors and software bugs.
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A Byzantine fault is any fault presenting different symptoms to different observers. A Byzantine failure is the loss of a system service due to a Byzantine fault in systems that require consensus. The objective of Byzantine fault tolerance is to be able to defend against failures of system components with or without symptoms that prevent other components of the system from reaching an agreement among themselves, where such an agreement is needed for the correct operation of the system. Remaining operationally correct components of a Byzantine fault tolerant system will be able to continue providing the system's service as originally intended, assuming there are a sufficient number of accurately-operating components to maintain the service.
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For instance, if nine generals are voting, four of whom support attacking while four others are in favor of retreat, the ninth general may send a vote of retreat to those generals in favor of retreat, and a vote of attack to the rest. Those who received a retreat vote from the ninth general will retreat, while the rest will attack (which may not go well for the attackers). The problem is complicated further by the generals being physically separated and having to send their votes via messengers who may fail to deliver votes or may forge false votes. Byzantine fault tolerance can be achieved if the loyal (non-faulty) generals have a majority agreement on their strategy.
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As VNFs replace traditional function-dedicated equipment, there is a shift from equipment-based availability to a service-based, end-to-end, layered approach.'NETWORK FUNCTIONS VIRTUALIZATION CHALLENGES AND SOLUTIONS', TMCNET webpage, Alcatel-Lucent Strategic paper, 2013'NFV: The Myth of Application- Level High Availability ', Wind River White Paper, May 2015 Virtualizing network functions breaks the explicit coupling with specific equipment, therefore availability is defined by the availability of VNF services. Because NFV technology can virtualize a wide range of network function types, each with their own service availability expectations, NFV platforms should support a wide range of fault tolerance options. This flexibility enables CSPs to optimize their NFV solutions to meet any VNF availability requirement.
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The single-failure hypothesis, dual-failure hypothesis, and tolerance against arbitrary synchronization disturbances define the basic fault-tolerance concept in a Time-Triggered Ethernet (SAE AS6802-based) network. Under the single-failure hypothesis, Time-Triggered Ethernet (SAE AS6802) is intended to tolerate either the fail-arbitrary failure of an end system or the fail-inconsistent-omission failure of a switch. The switches in Time-Triggered Ethernet network can be configured to execute a central bus guardian function. The central bus guardian function ensures that even if a set of end systems becomes arbitrarily faulty, it masks the system-wide impact of these faulty end systems by transforming the fail- arbitrary failure mode into an inconsistent-omission failure mode.
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This message triggers the execution of code within the chare to handle the message asynchronously. Chares may be organized into indexed collections called chare arrays and messages may be sent to individual chares within a chare array or to the entire chare array simultaneously. The chares in a program are mapped to physical processors by an adaptive runtime system. The mapping of chares to processors is transparent to the programmer, and this transparency permits the runtime system to dynamically change the assignment of chares to processors during program execution to support capabilities such as measurement-based load balancing, fault tolerance, automatic checkpointing, and the ability to shrink and expand the set of processors used by a parallel program.
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These restrictions work like microscopic fuses so that if a point-defect short-circuit between the electrodes occurs, the high current of the short only burns out the fuses around the fault. The affected sections are thus disconnected and isolated in a controlled manner, without any explosions surrounding a larger short-circuit arc. Therefore, the area affected is limited and the fault is gently controlled, significantly reducing internal damage to the capacitor, which can thus remain in service with only an infinitesimal reduction in capacitance. In field installations of electrical power distribution equipment, capacitor bank fault tolerance is often improved by connecting multiple capacitors in parallel, each protected with an internal or external fuse.
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A master-checker is a hardware-supported fault tolerance method for multiprocessor systems, in which two processors, referred to as the master and checker, calculate the same functions in parallel in order to increase the probability that the result is exact. The checker-CPU is synchronised at clock level with the master-CPU and processes the same programs as the master. Whenever the master-CPU generates an output, the checker-CPU compares this output to its own calculation and in the event of a difference raises a warning. The master-checker system generally gives more accurate answers by ensuring that the answer is correct before passing it on to the application requesting the algorithm being completed.
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The CUCU allows the ISS to communicate with Dragon and the CCP allows ISS crew members to issue basic commands to Dragon. In summer 2009, SpaceX hired former NASA astronaut Ken Bowersox as vice president of their new Astronaut Safety and Mission Assurance Department, in preparation for crews using the spacecraft. As a condition of the NASA CRS contract, SpaceX analyzed the orbital radiation environment on all Dragon systems, and how the spacecraft would respond to spurious radiation events. That analysis and the Dragon design – which uses an overall Fault tolerance triple redundant computer architecture, rather than individual radiation hardening of each computer processor – was reviewed by independent experts before being approved by NASA for the cargo flights.
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Ken Birman developed the virtual synchrony model in a series of papers published between 1985 and 1987. The primary reference to this work is "Exploiting Virtual Synchrony in Distributed Systems", which describes the Isis Toolkit, a system that was used to build the New York and Swiss Stock Exchanges, French Air Traffic Control System, US Navy AEGIS Warship, and other applications. Recent work by Miguel Castro and Barbara Liskov used the state machine approach in what they call a "Practical Byzantine fault tolerance" architecture that replicates especially sensitive services using a version of Lamport's original state machine approach, but with optimizations that substantially improve performance. Most recently, there was also created the BFT-SMaRt library,BFT-SMaRt.
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A brake-by-wire system, by nature, is a safety critical system and therefore fault tolerance is a vitally important characteristic of this system. As a result, a brake-by-wire system is designed in such way that many of its essential information would be derived from a variety of sources (sensors) and be handled by more than the bare necessity hardware. Three main types of redundancy usually exist in a brake-by-wire system: # Redundant sensors in safety critical components such as the brake pedal. # Redundant copies of some signals that are of particular safety importance such as displacement and force measurements of the brake pedal copied by multiple processors in the pedal interface unit.
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Fault tolerance is built into VOS from the bottom up. On a hardware level, major devices are run in lockstepped duplex mode, meaning that there are two identical devices performing the same action at the same time. (In addition, each device, or board, is also duplexed in order to identify internal board failures at a hardware level, which is why Stratus hardware can be defined as "lock stepped".) These boards are actively monitored by the operating system which can correct any minor inconsistencies (such as bad disk-writes or reads). Any boards which report an unacceptable number of faults are removed from service by the system; the duplexed board will continue operation until the problem is resolved via a hot-fix.
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The Distributed hash calendar is a distributed network of hash calendar nodes. In order to ensure a high availability service it is possible to have multiple calendars in different physical locations all of which communicate with each other to ensure that each calendar contains identical hash values. Ensuring that the calendars remain in agreement is a form of Byzantine fault tolerance To the right a 5 node calendar cluster is shown where each node communicates with every other node in the cluster and there is no single point of failure. Although each node has a clock the clock is not used for setting the time directly but as a metronome to ensure that the nodes “beat” at the same time.
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In order to guarantee safety (also called "consistency"), Paxos defines three properties and ensures the first two are always held, regardless of the pattern of failures: ; Validity (or non- triviality): Only proposed values can be chosen and learned. ; Agreement (or consistency, or safety): No two distinct learners can learn different values (or there can't be more than one decided value) ; Termination (or liveness): If value C has been proposed, then eventually learner L will learn some value (if sufficient processors remain non-faulty). Note that Paxos is not guaranteed to terminate, and thus does not have the liveness property. This is supported by the Fischer Lynch Paterson impossibility result (FLP) which states that a consistency protocol can only have two of safety, liveness, and fault tolerance.
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The problem of obtaining Byzantine consensus was conceived and formalized by Robert Shostak, who dubbed it the interactive consistency problem. This work was done in 1978 in the context of the NASA-sponsored SIFT project in the Computer Science Lab at SRI International. SIFT (for Software Implemented Fault Tolerance) was the brain child of John Wensley, and was based on the idea of using multiple general- purpose computers that would communicate through pairwise messaging in order to reach a consensus, even if some of the computers were faulty. At the beginning of the project, it was not clear how many computers in total are needed to guarantee that a conspiracy of n faulty computers could not "thwart" the efforts of the correctly-operating ones to reach consensus.
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Both databases Mnesia and CouchDB as well as Yaws (and also Mochiweb, Misultin, and Cowboy) are written in Erlang, so web applications developed for LYME/LYCE may be run entirely in one Erlang virtual machine. This is in contrast to LAMP where the web server (Apache) and the application (written in PHP, Perl or Python) might be in the same process, but the database is always a separate process. As a result of using Erlang, LYME and LYCE applications perform well under high load and if distribution and fault tolerance is needed. The query and data manipulation language of Mnesia is also Erlang (rather than SQL), therefore a web- application for LYME is developed using only a single programming language.
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Afterwards, Shostak joined the research staff in the Computer Science Lab (CSL) at SRI International (formerly the Stanford Research Institute) in Menlo Park, California. Much of his work there focused on automated theorem proving, and specifically on the development of decision procedure algorithms for mechanized proof of the kinds of mathematical formulas that occur frequently in the formal verification of correctness of computer programs. In collaboration with CSL's Richard L. Schwartz and P. Michael Melliar-Smith, Shostak implemented a semi-automatic theorem prover incorporating some of these decision procedures. The prover was used to verify correctness properties of an abstract specification of the SIFT (for Software Implemented Fault Tolerance) operating system and was later incorporated into SRIís Prototype Verification System.
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Riak is written in Erlang, a language that gives a system built-in support for distribution across a server cluster, fault tolerance, and an ability to absorb new hardware being added to the cluster without disrupting operations. Following the demise of Basho, the company assets were purchased by Bet365 and previously closed source components such as riak_repl (multi-data-centre replication) were released as open-source on github.com. Basho also offered Riak Cloud Storage (CS), an open source multi-tenant cloud storage database, built on the Riak platform, which integrated with private clouds and public clouds such as Amazon Web Services (AWS). It can be used by enterprises to power internal private clouds and by startups with an Amazon-compatible API for their own download service.
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Hypohamiltonian graphs arise in integer programming solutions to the traveling salesman problem: certain kinds of hypohamiltonian graphs define facets of the traveling salesman polytope, a shape defined as the convex hull of the set of possible solutions to the traveling salesman problem, and these facets may be used in cutting-plane methods for solving the problem.; ; . observes that the computational complexity of determining whether a graph is hypohamiltonian, although unknown, is likely to be high, making it difficult to find facets of these types except for those defined by small hypohamiltonian graphs; fortunately, the smallest graphs lead to the strongest inequalities for this application.. Concepts closely related to hypohamiltonicity have also been used by to measure the fault tolerance of network topologies for parallel computing.
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Finally fault tolerance among members of the distribution tree is accomplished through the use of timeouts and keepalives with actual data transmissions doubling as keepalives to minimize traffic. If a child node does not hear from its parent for a while, it routes a new subscribe message toward the root node of the tree, reattaching itself wherever it bumps into the tree for that topic. If a parent doesn't hear from a child for a timeout period, it drops the child from its list of children. (If this action causes its child list to become empty, the parent stops acting as a forwarder altogether.) The only remaining failure point is that of the root node, and Pastry itself automatically overcomes this.
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Quality-of-Data (QoD) is a designation coined by L. Veiga, that specifies and describes the required Quality of Service of a distributed storage system from the Consistency point of view of its data. It can be used to support Big Data management frameworks, Workflow management, and HPC systems (mainly for data replication and consistency). It takes into account data semantics, namely Time interval of data freshness, Sequence of tolerable number of outstanding versions of the data read before refresh, and Value divergence allowed before displaying it. Initially it was based in a model from an existing research work regarding vector-field Consistency, awarded the best-paper prize in the ACM/IFIP/Usenix Middleware Conference 2007 and later enhanced for increased scalability and fault-tolerance.
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The C/H/S scheme has been replaced by logical block addressing (LBA), a simple linear addressing scheme that locates blocks by an integer index, which starts at LBA 0 for the first block and increments thereafter. When using the C/H/S method to describe modern large drives, the number of heads is often set to 64, although a typical hard disk drive, , has between one and four platters. In modern HDDs, spare capacity for defect management is not included in the published capacity; however, in many early HDDs a certain number of sectors were reserved as spares, thereby reducing the capacity available to the operating system. For RAID subsystems, data integrity and fault-tolerance requirements also reduce the realized capacity.
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BiiN began in 1982 as Gemini, a research project equally funded by Intel and Siemens. The project's aim was to design and build a complete system for so-called "mission critical" computing, such as on-line transaction processing, industrial control applications (such as managing nuclear reactors), military applications intolerant of computer down-time, and national television services. The central themes of the R&D; effort were to be transparent multiprocessing and file distribution, dynamically switchable fault tolerance, and a high level of security. Siemens provided the funding through its energy division UBE (Unternehmensbereich Energietechnik), who had an interest in fault tolerant computers for use in nuclear installations, while Intel provided the technology, and the whole project was organised with alternate layers of Siemens and Intel management and engineers.
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Michel Raynal’s research contributions concern mainly concurrent and distributed computing, and more specifically: causality, distributed synchronization, fault-tolerance, distributed agreement (consensus) and distributed computability. His first book (on mutual exclusion algorithms in both shared memory and message-passing systems) is recognized as one of the first books entirely devoted to distributed algorithms. On the synchronization side, with Jean-Michel Hélary and Achour Mostéfaoui, Michel Raynal designed a very simple generic message-passing mutual exclusion algorithm from which can be derived plenty of token and tree-based mutex algorithms. On the causality side, with co-workers he produced a very simple algorithm for causal message delivery, and an optimal vector-clock-based distributed checkpointing algorithms, which established the theoretical foundations of distributed checkpointing, and the so-called communication-based snapshot.
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Although the distributed hash table functionality of Pastry is almost identical to other DHTs, what sets it apart is the routing overlay network built on top of the DHT concept. This allows Pastry to realize the scalability and fault tolerance of other networks, while reducing the overall cost of routing a packet from one node to another by avoiding the need to flood packets. Because the routing metric is supplied by an external program based on the IP address of the target node, the metric can be easily switched to shortest hop count, lowest latency, highest bandwidth, or even a general combination of metrics. The hash table's key-space is taken to be circular, like the key-space in the Chord system, and node IDs are 128-bit unsigned integers representing position in the circular key-space.
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In an enterprise server, a Caching SAN Adapter is a host bus adapter (HBA) for storage area network (SAN) connectivity which accelerates performance by transparently storing duplicate data such that future requests for that data can be serviced faster compared to retrieving the data from the source. A caching SAN adapter is used to accelerate the performance of applications across multiple clustered or virtualized servers and uses DRAM, NAND Flash or other memory technologies as the cache. The key requirement for the memory technology is that it is faster than the media storing the original copy of the data to ensure performance acceleration is achieved. A caching SAN adapter's cached data is not captive to the server which hosts the adapter and enables clustered enterprise servers to share the cache for fault tolerance and application performance acceleration.
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Source: The notion of Computational Intelligence was first used by the IEEE Neural Networks Council in 1990. This Council was founded in the 1980s by a group of researchers interested in the development of biological and artificial neural networks. On November 21, 2001, the IEEE Neural Networks Council became the IEEE Neural Networks Society, to become the IEEE Computational Intelligence Society two years later by including new areas of interest such as fuzzy systems and evolutionary computation, which they related to Computational Intelligence in 2011 (Dote and Ovaska). But the first clear definition of Computational Intelligence was introduced by Bezdek in 1994: a system is called computationally intelligent if it deals with low-level data such as numerical data, has a pattern-recognition component and does not use knowledge in the AI sense, and additionally when it begins to exhibit computational adaptively, fault tolerance, speed approaching human-like turnaround and error rates that approximate human performance.
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These properties of the genetic code make it more fault- tolerant for point mutations. For example, in theory, fourfold degenerate codons can tolerate any point mutation at the third position, although codon usage bias restricts this in practice in many organisms; twofold degenerate codons can withstand silence mutation rather than Missense or Nonsense point mutations at the third position. Since transition mutations (purine to purine or pyrimidine to pyrimidine mutations) are more likely than transversion (purine to pyrimidine or vice versa) mutations, the equivalence of purines or that of pyrimidines at twofold degenerate sites adds a further fault- tolerance. hydropathy. A practical consequence of redundancy is that some errors in the genetic code cause only a silent mutation or an error that would not affect the protein because the hydrophilicity or hydrophobicity is maintained by equivalent substitution of amino acids; for example, a codon of NUN (where N = any nucleotide) tends to code for hydrophobic amino acids.
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Multipath access to a RAID using Linux DM Multipath (Legend: "HBA" = Host bus adapter, "SAN" = Storage area network) In computer storage, multipath I/O is a fault-tolerance and performance-enhancement technique that defines more than one physical path between the CPU in a computer system and its mass-storage devices through the buses, controllers, switches, and bridge devices connecting them. As an example, a SCSI hard disk drive may connect to two SCSI controllers on the same computer, or a disk may connect to two Fibre Channel ports. Should one controller, port or switch fail, the operating system can route the I/O through the remaining controller, port or switch transparently and with no changes visible to the applications, other than perhaps resulting in increased latency. Multipath software layers can leverage the redundant paths to provide performance-enhancing features, including dynamic load balancing, traffic shaping, automatic path management, and dynamic reconfiguration.
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Unlike standard Private Branch Exchange telephone systems (PBX) designed for general office users, Trading turret system architecture has historically relied on highly distributed switching architectures that enable parallel processing of calls and ensure a "non-blocking, non-contended" state where there is always a greater number of trunks (paths in/out of the system) than users as well as fault tolerance which ensures that any one component failure can not affect all users or lines. As processing power has increased and switching technologies have matured, voice trading systems are evolving from digital time-division multiplexing (TDM) system architectures to Internet Protocol (IP) server-based architectures. IP technologies have transformed communications for traders by enabling converged, multimedia communications that include, in addition to traditional voice calls, presence-based communications such as: unified communications and messaging, instant messaging (IM), chat and audio/video conferencing. Some of modern trading turret models are optimised to integrate with PBX platform.
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Examples of such modifications include using various alternative drugs, omitting the cricoid pressure, or applying ventilation before the tube has been secured. The procedure is used where general anesthesia must be induced before the patient has had time to fast long enough to empty the stomach; where the patient has a condition that makes aspiration more likely during induction of anesthesia, regardless of how long they have fasted (such as gastroesophageal reflux disease or advanced pregnancy); or where the patient has become unable to protect their own airway even before anesthesia (such as after a traumatic brain injury). The induction drugs clasically used for RSI have short durations of action, wearing off after only minutes. This confers a degree of fault tolerance on the procedure when it is used in elective or semi-elective settings: if intubation is unsuccessful, and if the clinical condition allows it, the procedure may be abandoned and the patient should regain the ability to protect their own airway sooner than would be the case under routine methods of induction.
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Axiom 1：“There are many algorithms to reach the goal under the condition of given functions and performance.” These diversified heterogeneous algorithms are equivalent under the condition of given functions and performance. If it can be proven that union or intersection calculation results of feasible methods can still meet requirements of equivalent functions, no matter what scheduling strategies or dynamic combination of these heterogeneous algorithms are done, it will not change the given functions. Accordingly, the mapping relationship between the visual functions and the structure of the object is no longer unique or certain from the perspective of attackers, which can be used to achieve the active defense by the defenders. Axiom 2：“Everyone has diverse shortcomings while they rarely make the same mistakes on the same tasks in the same place at the same time.” This axiom provides a theoretical basis for applications of multi-mode ruling mechanisms of the heterogeneous redundancy architecture in fault tolerance, handling random failures of hardware and software in the field of reliability.
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Geac designed additional hardware to support multiple simultaneous terminal connections, and with Dr Michael R Sweet developed its own operating system (named Geac) and own programming language (OPL) resulting in a multi-user real-time solution called the Geac 500.500/800 The initial implementation of this system at Donlands Dairybought, later sold, by Neilson in Toronto1972: the first Geac 500 was installed at Donlands Dairy, running an order entry systemA year later the first Geac 800 was installed at Donlands led to a contract at Vancouver City Savings Credit Union ("Vancity") in Vancouver, British Columbia, to create a real-time multi- branch online banking system. Geac developed hardware and operating system software to link minicomputers together, and integrated multiple-access disk drives, thereby creating a multi-processor minicomputer with a level of protection from data loss. Subsequently, Geac replaced the minicomputers with a proprietary microcoded processor of its own design, resulting in vastly improved software flexibility, reliability, performance, and fault tolerance. This system, called the Geac 8000 was introduced in 1978.
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