Data Recovery
Different types of
media failures (physical or logical) require different recovery approaches.
Logical damage
When a logical damage occurs, specialised
software is required. This software reads the content of the drive and repairs
the structural errors which lead to the data loss. Reasons for logical data
loss:
- Damaged or unreadable master boot record (MBR)
- Deleted partition or partition table
- Reinstallation of the operating system (no backup)
- Restoration of the factory settings (no backup)
- Damaged or missing file system
- Deleted files
- Formatted drive
Damaged raid controller (losing raid configuration)
Physical damage
In case of physical damage, the situation is
much more complicated. Recovering data from failed drives must be performed in
a sterile environment. Drives can then safely be disassembled, tested and
fixed. Failed components must be replaced with matching and fully working spare
elements from a donor drive.
Donor drives sometimes need to be matched by
type, model, and production date. Physical damage to the platters forces the
engineer to focus the recovery efforts on the undamaged parts of the platter.
Such recovery usually uses up more than one set of donor drives and might extend the recovery time. After the physical recovery process is complete it is usually necessary to fix the logical structures as well. This process can be seen as similar to that of putting together a jigsaw puzzle (actually a more difficult process, given that the pieces in no way resemble the whole data set that we want to recreate). Perhaps a more accurate comparison would be putting together a jigsaw puzzle that has been chewed up by a dog!
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