Some modern hard disks incorporate free fall sensors to offer protection against head crashes caused by accidentally dropping the drive.
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Hardware and software failure are the two main causes for data loss. Background radiation, head crashes, and aging or wear of the storage device fall into the former category, while software failure typically occurs due to bugs in the code. Cosmic rays cause most soft errors in DRAM.
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However, this meant that there were 12 times more heads per drive, increasing the likelihood of head crashes. These flying heads were moved using a 16 position magnetic actuator. The actuator used four different magnets to create the 16 positions. The magnetic actuators were later replaced with hydraulic actuators, and later yet the hydraulic actuators were replaced with voice coil actuators.
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An absolute filter (HEPA filter) provided pressurized air to the cartridge, excluding most contaminants that would otherwise cause head crashes. When used on 16-bit systems such as the PDP-11, the drive stored roughly 1.2 megawords. When used on 12-bit systems such as the PDP-8, the drive stored 1.6 megawords (so roughly the same bit capacity, albeit formatted differently). Multiple drives were daisy chained from their controller using Unibus cabling; a terminator was installed in the farthest drive.
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Superman is unable to undo the deaths, but kills Mxyzptlk and then uses gold kryptonite on himself. Bizarro's final pre-Crisis appearance was in DC Comics Presents #97 (September 1986), which was also the final issue of that series. After being empowered by a hideously disfigured Phantom Zone sorcerer, Mr. Mxyzptlk destroys Zrfff and then causes the Bizarro world to implode, killing all its inhabitants. Bizarro's severed head crashes onto Clark Kent's desk and addresses Clark Kent before his simulated life ends.
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The combination of two technologies, GMR (Giant Magneto-Resistive) heads on 3.5-inch glass platters, are said to be largely to blame for the issues.MR heads on 2.5-inch glass platters had been reliably shipping for many years prior to the introduction of the Deskstar. A firmware update introduced wear levelling which avoids the heads dwelling too long over the same area thereby reducing the potential for head crashes. The same firmware update also fixed a possible data corruption due to a problem with S.M.A.R.T. background operations.
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Whiskers can be small enough to pass through air filters and can settle inside equipment, resulting in short circuits and system failure. Tin whiskers don't have to be airborne to damage equipment, as they are typically already growing in an environment where they can produce short circuits. At frequencies above 6 GHz or in fast digital circuits, tin whiskers can act like miniature antennas, affecting the circuit impedance and causing reflections. In computer disk drives they can break off and cause head crashes or bearing failures.
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A number of companies, including IBM and Burroughs, experimented with using large numbers of unenclosed disks to create massive amounts of storage. The Burroughs system uses a stack of 256 12-inch disks, spinning at a high speed. The disk to be accessed is selected by using air jets to part the stack, and then a pair of heads flies over the surface as in some hard disk drives. This approach in some ways anticipated the Bernoulli disk technology implemented in the Iomega Bernoulli Box, but head crashes or air failures were spectacularly messy.
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Data loss is an error condition in information systems in which information is destroyed by failures (like failed spindle motors or head crashes on hard drives) or neglect (like mishandling, careless handling or storage under unsuitable conditions) in storage, transmission, or processing. Information systems implement backup and disaster recovery equipment and processes to prevent data loss or restore lost data. Data loss can also occur if the physical medium containing the data is lost or stolen. Data loss is distinguished from data unavailability, which may arise from a network outage.
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Applications of DLC typically utilize the ability of the material to reduce abrasive wear. Tooling components, such as endmills, drill bits, dies and molds often use DLC in this manner. DLC is also used in the engines of modern supersport motorcycles, Formula 1 racecars, NASCAR vehicles, and as a coating on hard-disk platters and hard-disk read heads to protect against head crashes. Virtually all of the multi-bladed razors used for wet shaving have the edges coated with hydrogen-free DLC to reduce friction, preventing abrasion of sensitive skin.
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Earlier Jaz drives could overheat, and loading-mechanism jams could leave a disk stuck in the drive. Forcibly ejecting a stuck disk could destroy both drive and disk. Jaz drives are hard-disk technology, making them susceptible to contaminants in the drive; dust and grit could be introduced through a hole in the disk case where the motor drove the platters, and any dust built up on the external case could enter the drive with its next insertion. Additionally, the metal sliding door was capable of wearing the plastic, resulting in debris and head crashes.
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Apparently modifications were made by HP, in a program called the Performance Enhancement Project, raising 7935 performance 15% making it comparable to the older model. The HP 7935/33 achieved a track density of 625 tracks per inch (considered high at the time), achieving capacity using 7 platters, 13 data surfaces and 14 heads (one head and surface were used for servo data). The disc pack spun at 2694 revolutions a minute. Despite an extensive air purging spin-up sequence to prevent disc and head contamination, human users reportedly caused so many 7935 packs to have disc head crashes, many users simply purchased the 7933.
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The five Earths merge into a single shared universe, and the superheroes return to the present; only those present at the dawn of time remember the original realities. A cosmically empowered Anti-Monitor attacks again, transporting the new Earth to the antimatter universe and summoning a horde of shadow demons. He falls in a carefully planned counterattack, culminating in a battle with Kal-L (the Earth-Two Superman) Alexander Luthor of Earth-Three and Superboy of Earth- Prime, with help from New Gods adversary Darkseid. In this final battle the Anti-Monitor, reduced to a flaming head, crashes into a star and is killed by the Earth-Two Superman.
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Head crashes were a common problem on laptop computers, since they are subject to sudden motion. This has led to the development of technologies that detect sudden motion and take evasive action (for example by parking the heads), sometimes known as active hard-drive protection or "sudden motion sensing." In very old laptop designs, the head of a hard disk drive could become stuck if the laptop lost power, leaving the disk head in an unparked state and potentially leading to scoring of the drive if the laptop was moved. This is now an uncommon problem, as modern hard disk drives which are designed with portability in mind 'self-park' in the event of a power failure.
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Five disks removed from a dead IBM Deskstar 75GXP serial number YSG8T0976 manufactured by IBM in Hungary in July 2001 and failed in a server at the University of Florida in April 2003. Ten heads crashed so severely that almost all the magnetic media was removed from the flying part of the disks' surfaces revealing the transparent glass substrates. One disk in the upper left has some magnetic material on a portion of the head flying region. The drives were known for an unusually high rate of head crashes, due to the magnetic coating soon beginning to loosen and sprinkle off from the platters, creating dust in the hard disk array and leading to crashes over large areas of the platters.
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The disk read-and-write head is made using thin film techniques that include materials hard enough to scratch through the protective layers. A head crash can be initiated by a force that puts enough pressure on the platters from the heads to scratch through to the magnetic storage layer. A tiny particle of dirt or other detritus, excessive shock or vibration (such as accidentally dropping a running drive), can cause a head to bounce against its disk, destroying the thin magnetic coating on the area the heads come in contact with, and often damaging the heads in the process. After this initial crash, countless numbers of fine particles from the damaged area can land onto other areas and can cause more head crashes when the heads move over those particles, quickly causing significant damage and data loss, and rendering the drive useless.
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