----- Message from vindex+lists-linux-raid@xxxxxxxxxxx ---------
Date: Fri, 20 May 2011 15:32:44 +0200
From: Louis-David Mitterrand <vindex+lists-linux-raid@xxxxxxxxxxx>
Subject: why should I "initialize" JBOD disks?
To: linux-raid@xxxxxxxxxxxxxxx
Hi,
I just installed an Adaptec SAS 4805 and plugged 8 disks previously used
"as is" (no raid) on an LSI adapter but none are recongnized as boot
disk ("no bios installed").
It seems I need to "initialize" (read: wipe) them in the Adaptec bios
menu before being able to use them as JBOD.
What the fuck?!
The controller puts the configuration details for the disk on the disk
itself. That way you can plug the disk into another port or controller
of the same brand and it will simply work.
By my defintion JBOD should means "just get out of the way and let me
use my disks as they are".
Does that "initlialization" mean that disks become unusable when plugged
to an adapter of any other brand or model?
It will show as uninitialized.
What is the underlying format of JBOD disks. Can they be read by a
straight, non-raid adapter?
The configuration needs to be stored somewhere on the disk. Either at
the beginning or at the end (or a combination of both).
Hence I would expect the start of the disk to be shifted a bit (what
used to be block 0 on the disk while plugged into the RAID controller
will be some higher block) or the disk will "end" a bit before the
actual end of the disk.
So I'm pretty sure you can dd such a disk onto another one to rescue
the data given the right seek offset.
Alex.
----- End message from vindex+lists-linux-raid@xxxxxxxxxxx -----
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