You hard drive is the storehouse of all your data in your computer system; all useful data is stored on hard drive, which is probably one of the most valuable parts of your computer. You can have complete or partial data loss, if your hard drive fails, or crashes, or gets damaged. Your hard drive can fail or crash mainly due to two types of damages – physical damage and logical damage.
Physical damage to your hard drive may result in head crash, motor failure, losing the magnetic coating on the platter, disturbance in platters spinning at very high speed, ill-sounding mechanical failure noises (loud clicking, rattling, scratching), malfunctioning, literal failure of hard drive or hard drive crash, and consequently complete or partial data loss. Head crash is one of the types of physical damage that occurs when the read-write head of a hard disk drive touches its rotating platter resulting in catastrophic damage to the magnetic media on the platter surface. These physical damages to your hard drive may occur due to various reasons, such as –
- Dropping your computer or frequent jerks to your computer during travels - it can damage various parts in a hard drive such as read-write head, platter, etc.;
- Overheating of your hard drive – it can damage your hard drive's circuit board;
- Extensive usage – it can wear off your hard drive; Your hard drive can also get physically damaged due to
- Dust and dirt – it disturbs the functioning of HD, getting into the sealed drive unit and gets collected on magnetic surfaces, and gets stuck in the thin gap between the head.
However, these physical damages can be greatly prevent by keeping good care of your hard drive, handling it carefully, and keeping it well protected from dust.
Usually, for recovering the data from physically damaged hard drive, all physical damages are required to be repaired first. Some damages can be repaired by replacing parts in the hard disk. Sometimes, hard drive becomes usable, after repairing damaged hardware (if hard drive has no logical damage). Some of the hardware repair procedures may include – removing a damaged PCB (printed circuit board) and replacing it with a matching PCB from a healthy drive, changing the original damaged read/write head assembly with matching parts from a healthy drive, removing the hard disk platters from the original damaged drive and installing them into a healthy drive, and often a combination of all of these procedures. However, these hardware repair procedures require a great amount of technical knowledge and skills, and these should never be attempted, if you do not have the hardware or technical expertise required to accomplish these repairs.
Logical damage to your hard drive may cause hard drive failure or hard drive crash, and consequently complete or partial data loss. It can cause a number of problems, such as strange behavior, like, infinitely recursing directories, and drives reporting negative amounts of free space. Logical damage can occur due to various reasons, such as – virus attack thru internet that also affects other computers on the network and crash them, inadvertently deletion of important files in the registry, or installation of faulty software program. Logical damages can be greatly prevented by using journaling file systems, such as NTFS 5.0, ext3, and XFS.
For recovering the data from logically damaged hard drive, all logical damages are required to be repaired. Logical damages can be repaired using any of many software programs available on the market. Most operating systems come with at least a rudimentary repair tool for their native file systems; for instance Linux has fsck utility, Mac OS X has Disk Utility, and Microsoft Windows provides chkdsk. Some of the notable software used in data recovery from logically damaged hard drive include – The Coroner's Toolkit, The Sleuth Kit, TestDisk, ILook IXimager, DCFLdd, CHKDSK, and fsck. However, these software programs can never guarantee that no data loss will occur.
There are mainly two main techniques that are used to recover data from logical damage – Consistency checking and Zero-knowledge analysis. Often, in the case of data recovery from logically damaged hard drive, it is common to use a specialized boot disk, Live CD or Live USB containing a minimal operating system and a set of repair tools.