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Re: Recover a XFS on raid -1 (linear) when one disk is broken

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Subject: Re: Recover a XFS on raid -1 (linear) when one disk is broken
From: Jan Banan <b@xxxxxxxxxxxx>
Date: Sat, 17 Jul 2004 16:05:16 +0200
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I have a raid -1 (linear) on my RedHat Linux 9 system with XFS
1.2.0.  The raid consists of 4 disks where the last disk now seem to
be broken.

backups?
I have some quite old backups. I'd like to try retrieve more recent data if possible.

Is it possible to in some way mount this raid system so that I can
recover the files stored on the first 3 disks of this raid -1
(linear)?

you could replace the last disk with a sparse file and run xfs_repair,
my gut feeling is that it won't work very well though since files will
be spread over disks (maybe not badly, depends on access patterns) and
also metadata on broken disks will refer to non-broken blocks and
vice-versa

I suppose the best stradegy is to get a new disk of the same size and then try to copy the whole damaged disk with "dd" to the new disk and then try to startup the raid again and after that run xfs_repair. What arguments to "dd" would fit best in this case? I think I've read that "dd" will normally abort when it can't read from a damaged disk and the disk is quite big, 250 GB (Maxtor).

Since it is a 4 disk linear raid I hope most of the files are not spread over blocks on different disks since I suppose XFS (1.2.0) tries to store the files on blocks close to each other(?).

Anyone knows what normally has happened to a disk when you suddenly can not read from some parts of the disk? I get these kind of errors:

Jul 15 21:18:58 d kernel: hdh: dma_intr: status=0x51 { DriveReady SeekComplete Error } Jul 15 21:18:58 d kernel: hdh: dma_intr: error=0x40 { UncorrectableError }, LBAsect=243818407, high=14, low=8937383, sector=243818336 Jul 15 21:18:58 d kernel: end_request: I/O error, dev 22:41 (hdh), sector 243818336

Can I do something to make it better? The disk is only one year old but maybe the temperature has been a little bit to high in the computer box.

Best regards and thanks for any kind of hint!
Jan


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