[R114]Recovering Hard Disk Data

We have all heard of cases, and unfortunately many of us had to live through one as well; a hard disk crash on a computer. It's your worst nightmare. Even though disks are remarkably reliable, any electro-mechanical device will eventually suffer from the demand placed upon it and go wrong. We are used to hearing the term ?crash?, but where does it comes from and is there any chance on recovering your data?

A hard disk crash is normally the term given for the failure in which the read/write head touches the surface of the platter. The hard disk consists of a platter on which the data is stored. This is rotating with a reading head floating a microscopic distance above the platter. Imagine what happens when this head ?crashes? down on the platter. Nearly always there is damage to the head and the coating of the platter will be stripped away. This is what happens when your ?hard disk crashes?. However, there are many more hard disk failures that are commonly given the name ?hard disk crash?.

Alignment Failure and Head Failure.
The read head of the hard disk is positioned at such a microscopically precise position in order to read the data. If any head suffers positional problems as the result of mechanical wear, it will no longer be able to read the magnetic signals. The disk will fail, but as long as the platter is not damaged, it is very likely that a specialist can recover the data for you.

Media Failure.
All hard disks suffer failures during writing at some time. Normally this is not a problem. Modern disks use ?spare sectors?, which are used as a substitute when a failure occurs in a certain sector during writing. The disk will map out the ?bad sector? and use the ?spare sector? in its place. You will not notice anything at all as a user. However, after the number of failed sectors on the disk grows and the number of spare sectors decreases, you will start to see error messages being reported . Chances are that ?bad sectors? will appear in the most used parts of the disk and result in problems with accessing the file system. Even though the files are there, you no longer can access the data. The chances of data recovery are actually quite high, if the work is done by professionals.

Bearing Seizure.
Within the hard disk is a set of bearings that help the platter rotate smoothly at 10,000 rpm. A first sign of bearing failure can be that the disk becomes noisy. With a complete failure, the disk will stop rotating and will no longer operate.

Memory Failure.
When a disk is turned on, it will first load vital operational data into on-board memory. Any failure of the on-board memory devices can result in a disk failure, while your data might still be fully recoverable.

Data Failures.
These kinds of failures are often wrongly blamed on the disk, but usually due to some failure of the computer system or operating system. Information has become corrupted and sections of the file system can no longer be accessed.

Data recovery specialists are often able to recover data from disks that have suffered any of the above failures and success rates are very high. However, it can be very complex work in which case the costs might be quite high. In severe cases some data is lost forever, do not expect the specialist to be successful with data recovery from a surface that has been stripped by a real head crash. It is vital to have adequate backups, because failures do and will happen. Every a hard disk will eventually age and show signs of mechanical wear. Windows XP comes with a backup utility and a wizard that makes the whole process easy, Linux also provides a range or backup applications.

It has been said that there are two types of disks, a failed one and one that has not failed yet. So, do not forget to backup regularly to have the most current data safely stored away.