I have an 8 device raid6 array with 3 bad devices. Two
of the bad devices are recognized as spares belonging to
the array, the third device, the one that was most recently
an active sync part of the array somehow losts its superblock.
I'd like to try running the array with each of the bad devices
and see which makes an array with the least damaged filesystem.
One problem is how to add the device without the superblock.
I want to make sure it goes into position[0] in the array and
I'm not sure how to specifiy that with mdadm.
sdq1 is the device without the superblock, sdn1 and sde1 are
marked as spares but they were in sync recently.
To add sdq1 as device [0] even though it has no superblock would it be enough
to specify all the devices in the right order and leave the two that I'm not
experimenting with as missing?
mdadm -A /dev/md1 --force /dev/sdq1 /dev/sds1 /dev/sdab1 missing /dev/sdaa3 /dev/sdo1 /dev/sdu1 missing
And to try each spare in positions [3] and [7] a similar command, even though
the superblocks on the spares say [8] and [9]?
I want to avoid md doing any resyncing or recovery until I find the best
'bad' device to use.
Thanks for any help!
Andrew
PS This all happened when I upgraded the motherboard and the kernel version
at the same time, the resulting combination worked badly with my disk controllers
causing md to think drives were bad when they really weren't. Though how the
superblock vanished on the one drive is a mystery...
=======================================================
root # cat /proc/mdstat
md1 : inactive sds1[1] sde1[9] sdn1[8] sdu1[6] sdo1[5] sdaa3[4] sdab1[2]
2051009792 blocks
root # mdadm -A /dev/md1
mdadm: /dev/md1 assembled from 5 drives and 2 spares - not enough to start the array.
root # mdadm -A -v /dev/md1 2>&1 | grep added
mdadm: added /dev/sdab1 to /dev/md1 as 2
mdadm: added /dev/sdaa3 to /dev/md1 as 4
mdadm: added /dev/sdo1 to /dev/md1 as 5
mdadm: added /dev/sdu1 to /dev/md1 as 6
mdadm: added /dev/sdn1 to /dev/md1 as 8
mdadm: added /dev/sde1 to /dev/md1 as 9
mdadm: added /dev/sds1 to /dev/md1 as 1
root # mdadm -E /dev/sde1
/dev/sde1:
Magic : a92b4efc
Version : 00.90.00
UUID : 7fdb1d16:24896504:7df4ea3b:c7f0bf96
Creation Time : Sat Nov 12 12:43:57 2005
Raid Level : raid6
Device Size : 292969216 (279.40 GiB 300.00 GB)
Raid Devices : 8
Total Devices : 8
Preferred Minor : 1
Update Time : Wed Nov 30 08:12:57 2005
State : clean
Active Devices : 6
Working Devices : 8
Failed Devices : 2
Spare Devices : 2
Checksum : 2c0e61a6 - correct
Events : 0.930007
Number Major Minor RaidDevice State
this 9 8 65 9 spare /dev/sde1
0 0 65 1 0 active sync /dev/sdq1
1 1 65 33 1 active sync /dev/sds1
2 2 65 177 2 active sync /dev/sdab1
3 3 0 0 3 faulty removed
4 4 65 163 4 active sync /dev/sdaa3
5 5 8 225 5 active sync /dev/sdo1
6 6 65 65 6 active sync /dev/sdu1
7 7 0 0 7 faulty removed
8 8 8 209 8 spare /dev/sdn1
9 9 8 65 9 spare /dev/sde1
root # mdadm -E /dev/sdn1
/dev/sdn1:
Magic : a92b4efc
Version : 00.90.00
UUID : 7fdb1d16:24896504:7df4ea3b:c7f0bf96
Creation Time : Sat Nov 12 12:43:57 2005
Raid Level : raid6
Device Size : 292969216 (279.40 GiB 300.00 GB)
Raid Devices : 8
Total Devices : 8
Preferred Minor : 1
Update Time : Wed Nov 30 08:12:57 2005
State : clean
Active Devices : 6
Working Devices : 8
Failed Devices : 2
Spare Devices : 2
Checksum : 2c0e6234 - correct
Events : 0.930007
Number Major Minor RaidDevice State
this 8 8 209 8 spare /dev/sdn1
0 0 65 1 0 active sync /dev/sdq1
1 1 65 33 1 active sync /dev/sds1
2 2 65 177 2 active sync /dev/sdab1
3 3 0 0 3 faulty removed
4 4 65 163 4 active sync /dev/sdaa3
5 5 8 225 5 active sync /dev/sdo1
6 6 65 65 6 active sync /dev/sdu1
7 7 0 0 7 faulty removed
8 8 8 209 8 spare /dev/sdn1
9 9 8 65 9 spare /dev/sde1
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