If the head hits the disk's surface, a catastrophic head crash can result.
|
|
A head crash in a modern drive. Note circular scratch mark on the platter. A head crash A head crash is a hard-disk failure that occurs when a read–write head of a hard disk drive comes in contact with its rotating platter, resulting in permanent and usually irreparable damage to the magnetic media on the platter surface. It is most commonly caused by a sudden severe motion of the disk, for example the jolt caused by dropping a laptop to the ground while it is operating or physically shocking a computer.
|
|
Another cause of failure is a faulty air filter. The air filters on today's drives equalize the atmospheric pressure and moisture between the drive enclosure and its outside environment. If the filter fails to capture a dust particle, the particle can land on the platter, causing a head crash if the head happens to sweep over it. After a head crash, particles from the damaged platter and head media can cause one or more bad sectors.
|
|
A head crash, one type of disk failure A hard disk drive failure occurs when a hard disk drive malfunctions and the stored information cannot be accessed with a properly configured computer. A hard disk failure may occur in the course of normal operation, or due to an external factor such as exposure to fire or water or high magnetic fields, or suffering a sharp impact or environmental contamination, which can lead to a head crash. The stored information on a hard drive may also be rendered inaccessible as a result of data corruption, disruption or destruction of the hard drive's master boot record, or by malware deliberately destroying the disk's contents.
|
|
The most notorious cause of drive failure is a head crash, where the internal read-and-write head of the device, usually just hovering above the surface, touches a platter, or scratches the magnetic data-storage surface. A head crash usually incurs severe data loss, and data recovery attempts may cause further damage if not done by a specialist with proper equipment. Drive platters are coated with an extremely thin layer of non-electrostatic lubricant, so that the read-and-write head will simply glance off the surface of the platter should a collision occur. However, this head hovers mere nanometers from the platter's surface which makes a collision an acknowledged risk.
|
|
The system disengages the disk drive heads from the hard disk platters, preventing data loss and drive damage from a disk head crash. When the computer is stable, the drive operates normally again. A clicking noise can be heard when the sudden motion sensor activates. Broadly speaking, there have been two types of Sudden Motion Sensor.
|
|
Usually the system consists of accelerometers that alert the system when excess acceleration or vibration is detected. The software then tells the hard disk to unload its heads to prevent them from coming in contact with the platter, thus potentially preventing head crash. Many laptop vendors have implemented this technology under different names. Some hard-disk drives also include this technology, needing no cooperation from the system.
|
|
A British IBM 0665-30 hard disk exposed, possibly manufactured in 1985. (A head crash has occurred) The 0665 first shipped in October 1985 in the system unit for the PC AT (5170).1986 Disk/Trend Report – Rigid Disk Drives Developed under the code name "Pixie" at IBM Rochester, MN, it was a 5¼-inch HDD with capacities of 20, 30 and 44 MB.
|
|
Since most modern drives spin at rates between 5,400 and 15,000 RPM, the damage caused to the magnetic coating can be extensive. At 7,200 RPM, the edge of the platter is traveling at over , and as the crashed head drags over the platter surface, the read-write head generally overheats, making the drive or at least parts of it unusable until the heads cool. IBM RAMAC disk showing head crash damage.
|
|
Accelerometers are increasingly being incorporated into personal electronic devices to detect the orientation of the device, for example, a display screen. A free-fall sensor (FFS) is an accelerometer used to detect if a system has been dropped and is falling. It can then apply safety measures such as parking the head of a hard disk to prevent a head crash and resulting data loss upon impact. This device is included in the many common computer and consumer electronic products that are produced by a variety of manufacturers.
|
|
Like Tatsuo, he loves music and plays the saxophone from time to time. His Reflection Circuit gave him the same feelings as humans and a sense of right and wrong. Powered by 'super-gravitational energy', his killing techniques include "Laser Arm", "G-Kick", "Metal Tornado" spinning kick, "Head Crash" ram, "Plasma Punch", "Metal Bomber" punching attack from above, and "1000 Hand Punch". At the end of the series he defeats God Neros but in the process, his super- gravitational energy is greatly damaged, as a result whenever he moves longer, he will explode and the world will be destroyed by its impact.
|
|
The band has earned recognition and respect for being an entirely self-sustaining band. All the band's recordings are handled by guitarist Phil Douglas at his studio: The Hobo House (Douglas has also produced music by Latterman, RVIVR, Petal Head, Crash The Calm and Tender Defender), all the band's artwork is done by singer Jason Lubrano who also runs graphic design company Righteous Indignation with additional designs provided by drummer Gordon Lafler and all the band's merch, EP's and albums (except for 2013's The Constant One and 2017's You Can't Stay Here) is handled and distributed though bassist Mike Bruno's Dead Broke Rekerds (who has also released albums from Beach Slang, Samiam and Fifteen).
|
|
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.
|
|
The drive spins a PET film floppy disk at about 3000 rpm, 1 μm over a read-write head, using Bernoulli's principle to pull the flexible disk towards the head as long as the disk is spinning. In theory this makes the Bernoulli drive more reliable than a contemporary hard disk drive, since a head crash is impossible. The original Bernoulli disks came in capacities of 5, 10, and 20 MB. They are roughly 21 cm by 27.5 cm, similar to the size of a sheet of A4 paper. The most popular system was the Bernoulli Box II, whose disk cases are 13.6 cm wide, 14 cm long and 0.9 cm thick, somewhat resembling a 3-inch standard floppy disk but in 5-inch form factor. Bernoulli Box II disks came in the following capacities: 20 MB, 35 MB, 44 MB, 65 MB, 90 MB (late 1980s), 105 MB, 150 MB, and in 1993, 230 MB. There are five types of drives, grouped by the maximum readable capacity: 20 MB, 44 MB, 90 MB, 150 MB, and 230 MB. The interface is usually SCSI.
|
|
One RAMAC storage disk showing head crash damage The original 305 RAMAC computer system could be housed in a room of about 9 m (30 ft) by 15 m (50 ft); the 350 disk storage unit measured around . Currie Munce, research vice president for Hitachi Global Storage Technologies (which has acquired IBM's hard disk drive business), stated in a Wall Street Journal interviewLee Gomes, "Talking Tech" The Wall Street Journal, August 22, 2006 that the RAMAC unit weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. According to Munce, the storage capacity of the drive could have been increased beyond five megabytes, but IBM's marketing department at that time was against a larger capacity drive, because they did not know how to sell a product with more storage. RAMAC mechanism at Computer History Museum Programming the 305 involved not only writing machine language instructions to be stored on the drum memory, but also almost every unit in the system (including the computer itself) could be programmed by inserting wire jumpers into a plugboard control panel.
|
|