I seem to have been able to resolve this.

I tried force assembling the array with all the drives except for sda1
(the problematic device before) that way the array got assembled with
12 drives and one spare, enough so I could recover the array.

Still would want to know what might have caused these problems for the
first place, but I'm glad it seems to be working ok for now.

On Sat, Sep 7, 2013 at 10:56 PM, Garðar Arnarsson [off-list ref] wrote:

I am unable to start my raid6 array.

At first I got sda1 missing so I went ahead and re-added it and was
able to start the array. Then few minutes later I got 3 failed drives.

I shut down my server, checked all the sata and power cables and
booted up again.
The array did not start automatically so I tried to force assemble it.

sudo mdadm --assemble --verbose --force /dev/md1 /dev/sda1 /dev/sdb1
/dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1 /dev/sdh1 /dev/sdi1
/dev/sdj1 /dev/sdk1 /dev/sdm1 /dev/sdp1 /dev/sdq1
mdadm: looking for devices for /dev/md1
mdadm: /dev/sda1 is identified as a member of /dev/md1, slot 15.
mdadm: /dev/sdb1 is identified as a member of /dev/md1, slot 8.
mdadm: /dev/sdc1 is identified as a member of /dev/md1, slot 1.
mdadm: /dev/sdd1 is identified as a member of /dev/md1, slot 3.
mdadm: /dev/sde1 is identified as a member of /dev/md1, slot 6.
mdadm: /dev/sdf1 is identified as a member of /dev/md1, slot 9.
mdadm: /dev/sdg1 is identified as a member of /dev/md1, slot 10.
mdadm: /dev/sdh1 is identified as a member of /dev/md1, slot 0.
mdadm: /dev/sdi1 is identified as a member of /dev/md1, slot 11.
mdadm: /dev/sdj1 is identified as a member of /dev/md1, slot 7.
mdadm: /dev/sdk1 is identified as a member of /dev/md1, slot 5.
mdadm: /dev/sdm1 is identified as a member of /dev/md1, slot 14.
mdadm: /dev/sdp1 is identified as a member of /dev/md1, slot 2.
mdadm: /dev/sdq1 is identified as a member of /dev/md1, slot 4.
mdadm: ignoring /dev/sdq1 as it reports /dev/sda1 as failed
mdadm: added /dev/sdc1 to /dev/md1 as 1
mdadm: added /dev/sdp1 to /dev/md1 as 2
mdadm: added /dev/sdd1 to /dev/md1 as 3
mdadm: no uptodate device for slot 4 of /dev/md1
mdadm: added /dev/sdk1 to /dev/md1 as 5
mdadm: added /dev/sde1 to /dev/md1 as 6
mdadm: added /dev/sdj1 to /dev/md1 as 7
mdadm: added /dev/sdb1 to /dev/md1 as 8
mdadm: added /dev/sdf1 to /dev/md1 as 9
mdadm: added /dev/sdg1 to /dev/md1 as 10
mdadm: added /dev/sdi1 to /dev/md1 as 11
mdadm: no uptodate device for slot 12 of /dev/md1
mdadm: no uptodate device for slot 13 of /dev/md1
mdadm: added /dev/sdm1 to /dev/md1 as 14
mdadm: added /dev/sda1 to /dev/md1 as 15
mdadm: added /dev/sdh1 to /dev/md1 as 0
mdadm: /dev/md1 assembled from 11 drives and 2 spares - not enough to
start the array.

Any ideas what could have gone wrong and how I can possibly start the
array again?

-- 
Garðar Arnarsson
kerfisstjóri Giraffi sf.
gardar@giraffi.net
http://gardar.giraffi.net
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