| es huge storage capacities, hard disks provide | | | | crash. It is a failure of the disk in which the head |
| sequential access to the information stored on them. | | | | scrapes across the platter surface, often grinding |
| They have long life spans and data can be written, | | | | away the thin magnetic film causing data loss. |
| created, shifted, modified and erased any number of | | | | It is the main cause of data loss from the hard disk. |
| times on them. This makes them an irreplaceable | | | | Head crashes can be caused by external |
| storage device. | | | | contamination, electronic failure, sudden power failure, |
| HDDs were originally developed for use with | | | | physical shock, wear and tear, corrosion, or poorly |
| computers but their applications have expanded | | | | manufactured platters and heads. |
| beyond computers to include digital video recorders, | | | | In event of a hard disk crash the user should |
| digital audio players, personal digital assistants, digital | | | | immediately stop working on the computer. He should |
| cameras and video game consoles. | | | | not run a programme, write mails or browse the net or |
| All hard disks share the basic structure. A typical HDD | | | | even install DIY software. All these activities create |
| design consists of one or more flat circular disks called | | | | new files and can overwrite the existing files. Any |
| platters, on which magnetised data is recorded. | | | | overwritten data is lost forever. He should immediately |
| Traditionally, platters were made of a light aluminum but | | | | call a data recovery company. It needs expertise and |
| newer technology uses glass and/or ceramic platters | | | | experience to retrieve any data from a crashed hard |
| because they can be made thinner and have better | | | | disc and only professionals can do a good job of it |
| heat resistance. | | | | 2. Software Errors: Hard disks can loose data due to |
| Most drives have at least two platters and more | | | | software errors often triggered by the users |
| platters mean larger storage capacities. Each platter is | | | | themselves. These include an accidental deletion of a |
| magnetized on each side, so a drive with 2 platters | | | | file and emptying of recycle bin by mistake. Another |
| has 4 sides to store data. The platters are separated | | | | software error could be due to virus attack on the |
| by disk spacers and clamped to a rotating spindle that | | | | system while down loading data from internet or |
| turns all the platters in unison at a constant rate ranging | | | | through copying of corrupt CDs. |
| from 3,600 to 7,200 RPM. | | | | 3. Reformatting: A lot of times hard disks lose data |
| Information is written on a platter as it rotates past | | | | during reformatting of the disk. Format means to |
| mechanisms called read-and-write heads.They operate | | | | prepare a storage medium, usually a disk, for reading |
| very close over the magnetic surface. The | | | | and writing. When we format a disk, the operating |
| read-and-write head is used to detect and modify the | | | | system erases all bookkeeping information on the disk |
| information immediately under it. There is one head for | | | | and creates new internal address tables that it later |
| each magnetic platter surface on the spindle, mounted | | | | uses to locate information. All the data on the drive |
| on a common arm. | | | | can be lost if the reformatting attempt fails. Therefore |
| When one head is over a track, all the other heads | | | | it is essential to take a data backup before |
| are at the same location over their respective | | | | reformatting a hard disk drive. |
| surfaces. Typically, only one of the heads is active at a | | | | Most major hard disk vendors now support |
| time, reading or writing data. When not in use, the | | | | self-monitoring, analysis, and reporting technology |
| heads rest on the stationary platters at a | | | | (S.M.A.R.T.), which attempt to alert users to impending |
| predetermined position called the landing zone. When in | | | | failures. However, not all failures are predictable. |
| motion the spinning of the platters create air pressure | | | | Normal use eventually can lead to a breakdown in the |
| that lifts the heads off the platters. | | | | fragile structure of the device, making it essential for |
| Hard disk drives are considerably stable medium for | | | | the user to periodically back up data on a separate |
| data storage with good memory. They, however, have | | | | storage device. Failure to do so can lead to data loss. |
| some typical shortcomings leading to data loss: | | | | While it may be possible to recover lost information, it |
| 1. Head Crash: The space between the platter and the | | | | is normally an extremely costly procedure, with no |
| head is so minute that even one dust particle or a | | | | guaranteed success in the attempt. |
| fingerprint can disable the spin and lead to a head | | | | |