[CentOS] *very* ugly mdadm issue

Tue Sep 2 18:02:27 UTC 2014
Les Mikesell <lesmikesell at gmail.com>

On Tue, Sep 2, 2014 at 12:42 PM, Warren Young <warren at etr-usa.com> wrote:
> On 8/29/2014 14:26, m.roth at 5-cent.us wrote:
>> Note that we did this on *raw*, unpartitioned drives (not my idea).
>> I added
>> /dev/sdc to /dev/md4, and it started rebuilding.

> I know this isn't the answer you wanted, but it's probably the answer a lot
> of people *wanted* to give, but chose not to, going by the crickets.  (It's
> either that or the 3-day holiday weekend.)

I haven't used raw devices as members so I'm not sure I understand the
scenario.   However, I thought that devices over 2TB would not auto
assemble so you would have to manually add the ARRAY entry for
/dev/md4 in /etc/mdadm.conf containing /dev/sdd  and /dev/sdc for the
system to recognize it at bootup.

> Are you certain /dev/sdc is partially overwritten now?  What happens if you
> try to mount it?  If it mounts, go buy that second fresh disk, then set the
> mirror up correctly this time.

But sdd _should_ have the correct data - it just isn't being detected
as a raid member.   I think with smaller devices - or at least devices
with smaller partitions and FD type in the MBR it would have worked
automatically with the kernel autodetect.

   Les Mikesell
     lesmikesell at gmail.com