Re: MDADM RAID 6 Bad Superblock after reboot

[Wols Lists <antlists@youngman.org.uk>]

On 19/10/17 02:52, sfunk1x wrote:
> Thanks for the vote of confidence in not losing data here. As I
> mentioned above, I've set SELinux into permissive mode. I'm sort of at a
> loss as to what to do next. Since sd[fgh] don't have any superblock
> data, can I try to bring the array back online with 5 drives, then
> re-add the last three, with the hope that they sync? There obviously
> hasn't been any writes to the last three drives since the hard system
> reboot, so I'd hope their event numbers would be in sync?

Okay. First thing I'd try is temporarily get rid of mdadm.conf. You
don't actually need it. Then do "mdadm --stop /dev/md0" followed by
"mdadm --assemble --scan".

That'll tell mdadm to do a "best effort" to get everything running.
*Always* do an mdadm --stop between every attempt, because the quickest
way to mess up recovery attempts is to have the wreckage of a previous
attempt lying around.

If that doesn't work, then try assembling the array explicitly, ie
listing all the drives. I can't remember whether order is important - so
long as you don't specify --force it'll either work or fail, it won't do
any damage.

Beyond this point I'm getting out of my depth, I don't have the broad
experience so I'll have to step back and let others chime in, but
there's a good chance this will get your array back.

Cheers,
Wol