The Infinite Cat Project - Slide #1260: Puddle - Added 6-14-06

Data recovery is the process of salvaging data from damaged, failed, wrecked or inaccessible primary storage media when it cannot be accessed normally. Often the data is being salvaged from storage media formats such as hard disk drive, storage tapes, CDs, DVDs, RAID, and other electronics. This can be due to physical damage to the storage device or logical damage to the file system that prevents it from being mounted by the host operating system.

A wide variety of failures can cause physical damage to storage media. CD-ROMs can have their metallic substrate or dye layer scratched off; hard disks can suffer any of several mechanical failures, such as head crashes and failed motors; tapes can simply break. Physical damage always causes at least some data loss, and in many cases the logical structures of the file system are damaged as well. This causes logical damage that must be dealt with before any files can be rescued from the failed media.

Most physical damage cannot be repaired by end users. For example, opening a hard disk in a normal environment can allow dust to settle on the surface, causing further damage to the platters and complicating the recovery process. Furthermore, end users generally do not have the hardware or technical expertise required to make these repairs; therefore, data recovery companies are consulted. These firms use Class 100 cleanroom facilities to protect the media while repairs are being made, and tools such as magnetometers are used to manually read the bits off failed magnetic media. The extracted raw bits can be used to reconstruct a disk image, which can then be mounted to have its logical damage repaired. Once that is complete, the files can be extracted from the image.