Using ZFS as RAID0 - disk offline question

[Matthew Seaman]

On 04/06/2012 21:26, Kaya Saman wrote:
> You see if say a system board fails and both devices are named /dev/ad4
> and /dev/ad5 then a new system board gets put in and the device names
> changed to /dev/ad12 and /dev/ad13 my question is will the ZPOOL still
> exist? Will ZFS be intelligent enough to pick up the new device names
> via the disk ID's?

Yes, this should work just fine.  ZFS labels each disk with its own UUID
value, so you can pretty much shuffle the disks in any order across all
available disk slots, and ZFS will be able to put the zpool back together.

> Additionally if /dev/ad5 goes down, is it possible to keep using
> /dev/ad4 which is part of the 'downed' pool...?? Or would one need to
> replace the disk ad5 then the pool comes up again with only the
> information on ad4??

No.  A RAID0 zpool will be marked offline if any of the drives within it
fails.  You might be able to recover some data from remaining drives,
but not easily.  The surest way of getting anything back would be to go
to a specialist disaster recovery company, but expect to pay $$$ for it.
 Considering the price of hard drives nowadays, this would be a dumb
choice: you could easily convert your RAID0 to a RAID10 for much less
than it would cost you to try and recover from a broken RAID0.

Even if you do install a replacement disk, ZFS won't be able to rebuild
from your original drive.  You'ld have to wipe and rebuild from scratch.

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.
PGP: http://www.infracaninophile.co.uk/pgpkey


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