Hi Phil,
> A big stack trace suggests other problems in your system. Not that you
> don't have potential I/O error issues, but there might be a kernel problem.
>
> Please show "uname -a" and "mdadm --version".
These are the verisons I currently have, which the migration was
attempted with. The array was originally constructed years ago,
probably with older kernel/mdadm versions:
Linux muncher 3.0.0-32-server #51-Ubuntu SMP Thu Mar 21 16:09:49 UTC
2013 x86_64 x86_64 x86_64 GNU/Linux
mdadm - v3.1.4 - 31st August 2010
> The key thing to look for is a nonzero mismatch count in sysfs for that
> array. I'm not familiar with Ubuntu's script, so you might want to look
> by hand at some future point.
I'll have a look in future. I do also have mdadm running daily via
cron with "--monitor --oneshot" - do you know if this checks the
"mismatch_cnt" file and reports errors?
>> Also, while poking yesterday I noticed I was getting warnings of the
>> form "Device has wrong state in superblock but /dev/sde seems ok", so
>> I tried a forced assemble:
>> mdadm --assemble /dev/md0 --force
>>
>> Looks like it updated some info in the superblocks (and yes, I forgot
>> to save the original output first!), but the array remains inactive. I
>> have now sworn off poking around by myself, because I've no idea what
>> to do from here.
>
> Please show /proc/mdstat again, along with "mdadm -D /dev/md0".
---------------------------
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md0 : inactive sde[4] sdc[1] sdb[0] sdd[3]
7814054240 blocks super 1.2
unused devices: <none>
---------------------------
/dev/md0:
Version : 1.2
Creation Time : Sun Jul 17 00:41:57 2011
Raid Level : raid6
Used Dev Size : 1953512960 (1863.02 GiB 2000.40 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sat Jun 8 11:00:43 2013
State : active, degraded, Not Started
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric-6
Chunk Size : 512K
New Layout : left-symmetric
Name : muncher:0 (local to host muncher)
UUID : 830b9ec8:ca8dac63:e31946a0:4c76ccf0
Events : 50599
Number Major Minor RaidDevice State
0 8 16 0 active sync /dev/sdb
1 8 32 1 active sync /dev/sdc
3 8 48 2 active sync /dev/sdd
4 8 64 3 spare rebuilding /dev/sde
---------------------------
>> for x in /sys/block/sd[acde]/device/timeout ; do echo $x $(< $x) ; done
>> ----------------------------
>> /sys/block/sdb/device/timeout 30
>> /sys/block/sdc/device/timeout 30
>> /sys/block/sdd/device/timeout 30
>> /sys/block/sde/device/timeout 30
>
> Due to your green drives, you cannot leave these timeouts at 30 seconds.
> I recommend 180 seconds:
>
> for x in /sys/block/sd[bcde]/device/timeout ; do echo 180 >$x ; done
>
> (You should do this ASAP. On the run is fine.)
>
> You will need your system to do this at every boot. Most distros have
> rc.local or a similar scripting mechanism you can use.
>
> Phil
Done - thanks for the tip.
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