Question about LVM and RAID

Mikkel L. Ellertson mikkel at infinity-ltd.com
Thu Nov 29 17:17:41 UTC 2007


Kanwar Ranbir Sandhu wrote:
> Hi All,
> 
> I have an external drive cage which has been configured with two
> separate RAID 5 arrays.  I then used LVM to create two PVs, and then
> added the volumes together under one VG.  The whole shebang is mounted
> on one file system (/srv).
> 
> What would happen if one of the RAID arrays failed (e.g. two drives die
> in RAID 5 array 1)?  Would the data be safe, would I lose all data, or
> would I just lose the data that was on the failed array?
> 
> I believe I would only lose the data on the failed array, but a friend
> believe I would lose the whole lot.
> 
> Thanks in advance!
> 
> Regards,
> 
> Ranbir
Because they are one file system, it is hard to predict exactly what
you would lose, but in any case, recovering the data from the
remaining array would be interesting. I could be wrong, but I don't
believe there is anything in the LVM code that would prevent a file
from spanning the two RAID arrays making up the VG. So you can
figure you are going to lose any files that span the drives. (You
may be able to recover part of the file...)

You may want to start looking into LVM recovery tools now, before
you run into a problem. (And keep good backups.)

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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