Bad sector repair programs

How do hard disk repair programs work?

Background: Sometimes a hard disk will develop a fault commonly known as a bad sector. Basically, this is a part of the disk that has become unreadable and the data in that sector is generally inaccessible. Bad sectors on a hard disk can have various effects such as

making the computer run slowly
preventing access to certain files while other files remain OK
preventing access to the entire disk

Bad Sector 'Repair' Programs: These are pieces of software that typically overwrite areas of the disk that contain bad sectors. They work on the theory that overwriting the bad sectors with new data (usually zeroes) makes the sector more readable by the computer. Unfortunately if the files you want to retrieve contain a bad sector then running such a program will modify the original file and in some cases, if the damage is severe, will render the file inaccessible.

How they work: By reverse engineering a typical bad sector repair program Data Clinic have constructed a flow chart (partially reproduced here) to explain how one of these types of program works:

Use of these programs in the Forensics field: Hard drives that have been seized for investigation will sometimes fail to image successfully because of bad sectors. Because of the way that this type of program works, they must not be used to recover drives with bad sector problems as they will alter the contents of the hard drive. We are unsure of how many forensic investigators are aware of this.

Recovery of data from drives with bad sectors - What should I do?: Call the Data Clinic and talk your problem through with us on 0871 977 2525, or fill out our auto-form and we'll call you back

Links:

> Specific page: Maxtor DiamondMax 8 disk with bad sectors interrogated on an oscilloscope
> Specific page: Failure information and symptoms on Maxtor DiamondMax 8 (N40P) hard disks
> Specific page: Failure symptoms common to all slimline Maxtor hard disks
> General page: Common failures on Maxtor hard disk drives
> General page: Main data recovery information page

Please note that all modern hard disk drives are manufactured to very high standards, fail infrequently and have very similar rates of reliability.