Re: Manually hacking superblocks

[Neil Brown <neilb@suse.de>]

On Friday April 13, david@dgreaves.com wrote:
> Lasse Kärkkäinen wrote:
> > 
> > disk 0, o:1, dev:sdc1
> > disk 1, o:1, dev:sde1
> > disk 2, o:1, dev:sdg1
> > disk 3, o:1, dev:sdi1
> > disk 4, o:1, dev:sdh1
> > disk 5, o:1, dev:sdf1
> > disk 6, o:1, dev:sdd1
> > 
> > I gather that I need a way to alter the superblocks of sde and sdd so
> > that they seem to be clean up-to-date disks, with their original disk
> > numbers 1 and 6. A hex editor comes to mind, but are there any better
> > tools for that?
> 
..
> 
> I *THINK* you should try something like (untested):
> mdadm --assemble /dev/md0 --force /dev/sdc1 /dev/sde1 /dev/sdg1 /dev/sdi1
> missing /dev/sdf1 /dev/sdf1
> 
> The order is important and should match the original order.
> There's more you could do by looking at device event counts (--examine)

You will need a --create

--assemble ignores the order in which the devices are given.  It uses
the information on the drives.  Once you do a --add, you lose that
information.
It is good that you know the original order.  You --examine the
confirm the chunk size or any other details you might not be sure of
and recreate the array.  Leave one disk (the least likely to be
uptodate) as 'missing' and then try 'fsck -n' to ensure the data is
ok.

NeilBrown
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html