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macaddictg4
n00b
Joined: 25 Jan 2010
Posts: 1
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 Posted: Mon Jan 25, 2010 9:50 pm Post subject: RAID 5 Failure, No Hardware Disk Failures |
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For some reason my RAID 5 array of 5 disks would not assemble when I booted my system for the first time in the last couple months. I tried a few different things, and once using --assemble --scan I managed to get it to assemble 4 of the 5 disks and I could see the data (this happened after I had updated mdadm to the latest version). I then rebooted the system to verify that everything was working fine, and again it would not be recognized.
Eventually, I followed the advice from http://www.linuxquestions.org/questions/linux-server-73/software-raid-5-md-recovery-using-mdadm-551732/. I ran something similar to this command:
| Code: | | mdadm --create /dev/md0 --level=5 --raid-devices=5 /dev/sd[b-f]* |
Similar because my actual drives were sdb, sdc, sdd, sde, and sdg, but I can't remember the regular expression for that offhand.
At any rate, it "re-created" the raid array, and is saying that drives b-e are drives 0-3 and that drive g is a spare (this is not the case, they were all 5 part of the working array). The recreation was instantaneous, so I don't think that anything has been overwritten except maybe some superblock data. All of my regular data should still be intact on the drives, but when md0 assembles (no errors) and I try to mount it, it can't read the filesystem (ext3) and says there may be an issue with the superblock.
Is there any way that I can recover the old persistent superblock for the RAID volume? In my mdadm.com I have it building using the UUIDs, so maybe I can "re-create" with that instead of drive letters?
At this point I'm terrified about losing all my data, if I haven't already, so I wanted to get suggestions from those much more knowledgeable than myself before I start trying things again next week! |
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fangorn
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Joined: 31 Jul 2004
Posts: 1886
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| Posted: Tue Feb 02, 2010 3:06 pm Post subject: |
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http://www.gagme.com/greg/linux/raid-lvm.php#failure
You should have identified the drive failing, manually mark it as failed if necessary, and rebuilt the RAID5.
AFAIK you built a new RAID5 instead, overwriting all the administrative data. Maybe a professional data recovery company can make the data readable again, but I doubt a non-professional like us has a chance. 
Maybe a mail to the mdadm mailing lists could give you a more precise answer if there is a way to "guess" RAID parameter settings (like there is one to guess deleted partition tables using testdisk or gpart).
Keep in mind the golden rule:
"RAID is not a replacement for backups."
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