> -----Original Message-----
quoted text
> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
> owner@vger.kernel.org] On Behalf Of Pierre Vignéras
> Sent: Sunday, May 16, 2010 10:41 AM
> To: linux-raid@vger.kernel.org
> Subject: mdadm: failed devices become spares!
> 
> Hi,
> 
> I encountered a critical problem with mdadm that I submitted to the Debian
> mailing list (it's a debian lenny/stable). They asked me to submit this to
> you. So that's what I do.
> 
> To prevent duplication of description/information, I give you the URL of
> that
> bug description:
> 
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=578352
> 
> If you prefer the full stuff to be copy/pasted to that mailing list, just
> ask
> for it.
> 
> Note: that bug happened again today, on another RAID array. So the good
> news
> is that it is somewhat reproducible! The bad news, is that unless you have
> a
> magic solution, all my data are just lost (half of it was in the backup
> pipe!)...
> 
> Thanks for any help, and regards.
> --
> Pierre Vignéras

	It's not quite clear to me from the link whether your drives are
truly toast, or not.  If they are, then you are hosed.  Assuming not, then
you need to use 

`mdadm --examine /dev/sdxx` and `mdadm -Dt /dev/mdyy`

	to determine precisely all the parameters and the order of the block
devices in the array.  You need the chunk size, the superblock type, which
slot was occupied by each device in the array (this may not be the same as
when the array was created), the size of the array (if it did not fill the
entire partition in every case), the RAID level, etc.  Once you are certain
you have all the information to enable you to re-create the array, if need
be, the try to re-assemble the array with

`mdadm --assemble --force /dev/mdyy`

	If it works, then fsck the file system.  (I think I noticed you are
using XFS.  If so, do not use XFS_Check.  Instead, use XFS_Repair with the
-n option.)  After you have a clean file system, issue the command

`echo repair > /sys/block/mdyy/md/sync_action`

	to re-sync the array.  If the array does not assemble, then you will
need to stop it and re-create it using the options you obtained from your
research above and adding the --assume-clean switch to prevent a resync if
something is wrong.  If the fsck won't work after re-creating the array,
then you probably got one or more of the parameters incorrect.

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