Re: reconstructing raid5 with bad sectors

[Ross Vandegrift <ross@willow.seitz.com>]

On Mon, Aug 04, 2003 at 10:08:15AM -0700, dean gaudet wrote:
> is there an offline tool which can reconstruct such an array?  or even an
> offline tool which already has the parity calculation code and such which
> i could extend to support such reconstruction?
> 
> i considered copying the two bad disks with "dd conv=noerror,sync", which
> would stop the kernel from marking the drives as bad, but that seems a bit
> less than ideal because i really would like to reconstruct the bad stripes
> using the 3 valid copies and not include an all-zeroes copy created by dd.

dd_rescue sounds like your friend - it'll let you make raw backups of
the partitions, but instead of quitting on errors, it'll keep going
until it passes the bad areas.  You'll probably need a few disks to use
as dd_rescue targets, but once you have images of the needed partitions,
rebuild should work fine (assuming of course, that you're correct in saying
the errors never overlap).

-- 
Ross Vandegrift
ross@willow.seitz.com

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