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RAID 5 Multiple crash

Posted on 2004-08-09
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Last Modified: 2010-04-03
We have a Dell PV 220S SCSI Storage. We configured 8 hard disks with RAID5 and leaving one as a Hot Spare. Due to heat problems there was a three hard disk crash.

One of our administrators reconfigured the RAID and initialized it.

My Question: Is there a way to recover the data which was on it. We have lost almost 70 GB of data files.
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Question by:ccsenet
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InteraX earned 60 total points
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Hi ccsenet,

At this point it is looking bleak. The only people I know of who can do this sort of service is a company call OnTrack. Their prices aren't cheap. A 5 disk array which needed to be recovered for a customer I was dealing with about 5 years ago cost £15000. This included free new HDD's.

As the RAID array has been re-initialised, you may find that data has been irrecoverably lost.

My advice, 1. Power Down the system and leave it OFF, 2. Call OnTrack or someone similar, 3. Get ready to pay if you really need the data.

http://www.ontrack.com/

Good luck.
;-)
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by:EvilAardvark
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If you lost 3 of 8 drives in RAID 5, with only one spare, you're out of luck.

There's no way to fully rebuild your disk array without resorting to data recovery, which as said above is VERY expensive.  With 8 drives, the smarter thing to do would've been to use RAID10, which provides only 2/3 the storage of your RAID5+1Spare, but you can lose up to 4 drives (assuming you don't lose any pair) without any data loss, and it has much better performance than RAID5 in such a format.  

I'd advise you to institute a regular backup schedule (weekly at least), and migrate over to RAID 10 or 0+1

Info on Raid 0+1
http://www.acnc.com/04_01_0_1.html

Info on Raid 10
http://www.acnc.com/04_01_10.html



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by:ccsenet
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I have requested a quote from ontrack.com. I am waiting for their response.

Regarding RAID 10, is it not a requirement that the RAID controller (Dell PERC3 DC) should support RAID 10. It was supporting RAID5 configuration already

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by:cazzer
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Don't want to sound patronising - but surely you have a tape backup on a server like that??
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by:pjedmond
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Welcome to discovering the importance of backups.

RAID recovery just makes data recovery even more difficult than straight forward drive recovery, although it does increase the chances of recovering the data.

Correct procedure for this:

1.     Shutdown the system to prevent any more writes! More writes makes recovery more difficult!
2.     Remove ALL the original drives and label them.
3.     Image EVERY original drive onto a new drive. In the event of horrible sounds -stop - leave it to an expert!
4.     Put original drives somewhere safe in case of need of data recovery.
5.     Some people even make another copy of ALL the drives to have a spare 'referrence' copy of the drives.
6.     Install (preferably into the original system), and start the data recovery work.

I expect that this is almost exactly what ontrack does as it is the system that I use, but be warned, data recovery is mind numbingly boring and tedious. That's why we charge so much for it. If you get as far as point 6 above, then you have some hope of recovering some of that extra 70GB of data files with data recovery software that is readily available off the internet.

If the disc heads have crashed and there is horrible noises etc - leave it to the experts, you will only cause further damage to data.
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by:ccsenet
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Thanks to all of you. Right now I am skipping the recovery part. But all the answers will be of great use for me for a next crash.

Yes our backup has been having problems since a long time (permissions, too many files etc.). But now hopefully it will be fine.

Probably it will be more helpfule if pjedmond can provide a document with the complete recovery procedure with all details if possible. it will be useful not only for me but for others who face a problem in the future
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