วันจันทร์ที่ 8 มีนาคม พ.ศ. 2553

Hard drives : Data Recovery FileWhether you store files on a hard drive, floppy disk, or other external storage device like a Zip Drive, USB drive, compact flash card, or other media, the way in which the computer stores your data is essentially the same. For the purpose of this article will talk about data recovery for hard drives but the principals can be applied to most storage media.
A hard drive contains a number of disks called 'platters'. These platters are coated with a magnetic substance. The platters spin at high speed under an mechanical arm (the 'actuator' arm) that moves backwards and forwards over the surface of each platter. On the end of this metallic arm is a small copper wire. The computer sends a pulse through this wire which changes the state of the magnetic surface of a platter as it passes underneath. In this way the files that you store on your computer are encoded into the magnetic substance.

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DEFINITION - A hard disk is part of a unit, often called a 'disk drive,' 'hard drive,' or 'hard disk drive,' that stores and provides relatively quick access to large amounts of data on an electromagnetically charged surface or set of surfaces. Today's computers typically come with a hard disk that contains several billion bytes (gigabytes) of storage.
A hard disk is really a set of stacked 'disks,' each of which, like phonograph records, has data recorded electromagnetically in concentric circles or 'tracks' on the disk. A 'head' (something like a phonograph arm but in a relatively fixed position) records (writes) or reads the information on the tracks. Two heads, one on each side of a disk, read or write the data as the disk spins. Each read or write operation requires that data be located, which is an operation called a 'seek.' (Data already in a disk cache, however, will be located more quickly.)
A hard disk/drive unit comes with a set rotation speed varying from 4500 to 7200 rpm. Disk access time is measured in milliseconds. Although the physical location can be identified with cylinder, track, and sector locations, these are actually mapped to a logical block address (LBA) that works with the larger address range on today's hard disks.
Hard drives are complex. They have a circuit board and a number of moving parts. In terms of hard drive data recovery, the first thing that you must evaluate is whether it is a hardware problem that is stopping you from accessing your data. Common hardware problems include a faulty circuit board or problems with the actuator arm.
hard drive
A faulty circuit board is characterize by a drive that does not 'spin up', meaning that platters are not turning underneath the copper wire. A faulty actuator arm or more serious mechanical error is characterize by an abnormal clicking noise or a grinding noise. The best advise in determining whether you have a hardware problem is to listen to the sound of your hard drive. If you cannot hear the platters spinning (i.e. it is quiet when it is turned on) or you hear more serious noises then you should stop using the drive immediately and you will need to send your drive to a hardware data recovery service.
Hardware data recovery can be expensive because technicians may need to disassemble your hard drive to fix the problem. Hard drive data recovery is usually done in a 'clean room' as hard drives are sealed to avoid errors caused by dust or other particles. Also hard drives are finely tuned machinery and it takes specialist equipment to read the platters from a physically damaged drive.
If you are sending your hard drive to a data recovery specialist then you should attempt to obtain an upfront estimate of fees (although you will rarely get one), ask that if you send your hard drive for quotation purposes will they send it back to you in the same condition if you choose not to use the service, and make sure you send it to a reputable company as you may only get one chance at hard drive data recovery.