I have lost 2 of 3 mdadm RAID5 disks.
How can i recover whatever files are available on the remaining one disk?
Sundeep
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You can't, not without paying alot of money to companies that specializes in this kind of stuff.– OrphansCommented Jan 26, 2018 at 10:19
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1Or at all, start with understanding the very basics of what R5 does, oh and stop using R5 while you're at it.– Chopper3Commented Jan 26, 2018 at 10:30
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2 Answers
RAID5 provides protection from single disk loss.
The only suggestion I can give you, apart to restore from backup, is to run testdisk/photorec against the single disk do you have. For files which are smaller than RAID chunk size, you have a small possibility to recover something.
answered Jan 27, 2018 at 11:15
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photorec is indeed recovering some file (some whole and other in chucks), thanks for the information. Commented Jan 27, 2018 at 14:31
RAID 5 distributed data over stripes. In your case, each stripe consists of two data segments and a redundancy segment calculated from both data segments. The distribution of the segments is rotated over the disks from stripe to stripe to provide an even workload for each disk.
With only a single drive left, you've got one third of these segments. These alternate as
- data segment from the beginning of one stripe
- data segment from the end of another stripe
- rendundancy segment for a third stripe
The redundancy segment is useless - you don't have any of the data segments you'd need to reconstruct the other data segment.
Only very small files could be reconstructed from these segments - those that fit into a single segment. However, the file system structure is lost, so it's (practically) impossible to tell which segment belonged to a certain file other than guessing from its contents.
Essentially, take a disk editor and see what you can find. There's nothing more anyone can do.
RAID doesn't replace backups.
