Re: Mdadm device reassignment

[Andrew Reid <reidac@bellatlantic.net>]

> Hi all, I just installed the new stable Squeeze system, and moved over a
> raid5 from an older system. For some reason, it now wants to mount as md127
> instead of md0. I've been unable to map it back to md0.

[ Details elided...]

> > root@jupiter:~# mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 /dev/sdd1
> > /dev/sde1
> > mdadm: /dev/md0 has been started with 4 drives.
> > root@jupiter:~# cat /proc/mdstat
> > Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
> > [raid4] [raid10]
> > md0 : active (auto-read-only) raid5 sde1[0] sdb1[3] sdd1[2] sdc1[1]
> > 
> >       4395407808 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
> > 
> > unused devices: <none>
> 
> This works fine, until reboot, at which point we're back to md127. In
> 
> /var/log/syslog, I find this little oddity:
> > Feb 17 15:33:35 jupiter mdadm[1580]: DeviceDisappeared event detected on
> > md device /dev/md0
> > Feb 17 15:33:35 jupiter mdadm[1580]: NewArray event detected on md device
> > /dev/md127
> 
> The whole thing has me pretty stumped, what am I missing?

  I have no explanation for how you got there, but the config getting
re-set at reboot is probably because there's residual weirdness in the
initramfs. 

  Next time, after you fix it, try setting /etc/mdadm/mdadm.conf to 
reflect the desired config (I usually do this by putting the
output of "mdadm --query --detail --scan", leaving out the 
"metadata=<value>" bit), re-run update-initramfs, and then reboot.

  This may clear it, whatever it is.

  For the record, I've done a squeeze upgrade on a system with
software RAID, and didn't have any issues, so it's not like it's
doing it to everyone.

					-- A.
--
Andrew Reid / reidac@bellatlantic.net