RAID 0 Data Recovery.
Data Recovery from a RAID 0 system is conducted in very much the same manner as a single disk recovery. The RAID 0 element only adds to the complexity of the recovery as we have potentially two hard disk drives requiring laboratory attention. Once the faults with the hard disks have been overcome we can then concentrate on the reconstruction process and data extraction.
RAID 0 System failures.
RAID 0 is a Hard Disk Drive configuration without redundancy. If any hard disk drive in a RAID 0 array fails, the whole array fails and the system will not be able to read or write files.
Data from individual disks can be recovered but the data is useless unless it can be reconstructed properly.
Every RAID 0 implementation has a unique set of configuration parameters and reconstruction following corruption is a complex task.
Datlabs technicians specialize in rebuilding RAID 0 disk arrays using a variety of tools, test gear and laboratory facilities to accomplish the task. Datlabs have also developed propriety applications to specifically facilitate the reconstruction of RAID 0 arrays.
RAID 0 Configuration.
Merely as a help to understanding how a RAID O operates and why special assistance is needed when a disk drive fails it is worthwhile exploring how data is stored on RAID 0 configured disks.
Raid 0 arrays are built for performance. Instead of reading/writing specific files to one specific hard disk, RAID 0 arrays read/write files to multiple hard disks in parallel. The process of fracturing files and writing them to multiple hard disks is called “striping.” e.g.
As a demonstration of striping :- A text file of four characters “ABCD” and a RAID 0 of two disks (stripe width of two) with a stripe/block size of four bits (equal to one half of a character).
The text in the file can be shown as:-
The file is stored as follows:
The first block of four bits (first half of letter A) is written to disk 1 and the second block of four bits (second half of letter A) is written to disk 2. This pattern will repeat until all bits are written.
In this example half of the file is on disk 1 and the other half is on disk 2. Notice that the file is not split down the middle (down the middle would have “AB” on disk 1 and “CD” on disk 2). Half of each character is stored on each disk.
Now consider what happens when a disk fails and the data from each disk is recovered.
Disk 1 by itself contains the text “DD” and disk 2 contains a special character called “Device Control 2” and the number 4. Obviously, the data from each disk is garbage unless it’s reconstructed in the proper order. The array must be reconstructed properly by assembling alternating blocks from disk 1 and disk 2 like this: