Re: Recovering RAID5 with 2, actually 1, faulty disks.

[Phil Turmel <philip@turmel.org>]

On 11/25/2015 12:32 PM, Semyon Enskiy wrote:

> Does you think, that problem is that "Raid Devices : 10", but
> "Array State : AAAAAAAA.A.", where the extra, 11th, device is sdj3, which
> was rejected from system in past, but record about it leave in superblock?

No.  It just can't get past the fact that your array is double-degraded,
even though it isn't really, once the revert succeeds.

At this point, I don't see a way out without --create.  Fortunately, we
have complete details on your array, so we can supply the correct paramters:

mdadm --stop /dev/md3

mdadm --create --assume-clean --chunk=512 --data-offset=262144 \
  --level=5 --raid-devices=10 --metadata=1.2 /dev/md3 \
  /dev/sd{f,i,h,g,d,e,b,c}3 missing /dev/sdj3

Note that you cannot use [] notation -- it doesn't maintain the order of
the letters.  The keyword 'missing' takes the place of /dev/sda3.  It's
possible it would be fine, but I'd rather not risk it.

You should be able to access the content at this point.  Copy out any
super-critical files.  Then add sda3:

mdadm --add /dev/md3 /dev/sda3

This should initiate the rebuild.

Update your mdadm.conf file to use the new UUID, and update your initramfs.

Phil