Re: superblock error after power failure ---on an old system

[Neil Brown <neilb@suse.de>]

On Sat, 24 Apr 2010 06:18:57 -0500
Wierdl Máté <wierdlmate@gmail.com> wrote:

> Hello,
> 
> I have an old Dell Poweredge 2500 server running Fedora Core 3. The
> server  had one of its power units failed, and (I think) as a result,
> the raid arrays got damaged: three of them stayed alive (though
> degraded), but one is not accessible. Unfortunately, the server only
> has a floppy drive which doesn't work now, and so I cannot get any
> files, command outputs directly off the box.  I copy it all from the
> screen.
> 
> The array I cannot access is md3. It has the shared libraries on it so
> many commands do not work. In particular, I cannot have remote access
> to the box.
> 
>  The output of
> 
> mdadm -Es
> 
> is (I am not copying the UUIDs)
> 
> ARRAY /dev/md0 level=raid1 num-devices=2 devices=/dev/sdb2,/dev/sdc2
> ARRAY /dev/md2 level=raid1 num-devices=2 devices=/dev/sda6,/dev/sdc3
> ARRAY /dev/md3 level=raid5 num-devices=3 devices=/dev/sda3,/dev/sdb1,/dev/sdc1
> ARRAY /dev/md1 level=raid1 num-devices=2 devices=/dev/sda1,/dev/sda2
> 
> Also
> 
> md0  mounted at /
> md2 mounted at /var
> md1  mounted at /boot
> md3 should be mounted at /home
> 
> # cat /proc/mdstat
> Personalities: raid1 raid5
> md1: active raid1 sda2[1] sda1[0]
>          104320 blocks [2/2] [UU]
> 
> md2: active raid1 sda6[0]
>          513984 blocks [2/1] [U_]
> 
> md0: active raid1 sdc2[1]
>         1534080 blocks [2/1] [_U]
> 
> unused devices: none
> 
> # mdadm --detail /dev/md3
> mdadm: md device /dev/md3 does not appear to be active
> 
> At somebody's suggestion I tried
> 
> mdadm --assemble --scan /dev/md0
> 
> and got
> 
> /dev/sda has no superblock - assembly aborted
> 
> Then tried
> 
> mdadm  --force --run /dev/md3
> 
> and got
> 
> failed to run array /dev/md3: Invalid argument
> 
> I finally tried
> 
> # mdadm --assemble /dev/md3 /dev/sda3 /dev/sdb1 /dev/sdc1
> mdadm: device 1 in  /dev/md3 has wrong state superblock, but /dev/sdb1 seems ok

That looks close.  Just add "--force" to that and it will probably get
you going.

NeilBrown


> 
> Thanks for any help. I certainly would give remote access to a helping
> hand, but unfortunately the box cannot run sshd: the shared libraries
> are on the md3 array.
> 
> Máté
> 
> Máté Wierdl
> Dept of Math Sci, Univ of Memphis
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