* RAID5, 2 out of 4 disks failed, Events value differs too much
@ 2006-12-05 8:48 Bodo Thiesen
2006-12-08 0:34 ` Corey Hickey
0 siblings, 1 reply; 2+ messages in thread
From: Bodo Thiesen @ 2006-12-05 8:48 UTC (permalink / raw)
To: linux-raid
Hi, I have a little problem:
Some hours ago the second of four disks were kicked out of my RAID5 thus rendering it unusable. As of my current knowledge, the disks are still working correctly (I assume a cable connection problem) but that's not the problem. The real problem is, that the first failed disk has an event value of 9102893, the second failed disk has a value of 9324862 and the other two disks have a value of 9324869. In this case, what is the best to do to recover the RAID? Because just recreating the array with the 9324862-disk and the two 9324869-disks and later hotadding the 9102893-disk, is just unclean and as I understood it, this would trigger some silent data failures. Is there a chance to prevent this data failures to happen at all, or is it at least possible to tell, where this error(s) are (so I can manually check the data and take appropriate steps)? Remember that I still have the data from the first failed disk, from which parts may still be relatively up to date.
Has anyone had this problem already and found a nice solution for this?
Regards in advance, Bodo
mdadm -E on all affected disks:
--> please bite here <---> please bite here <---> please bite here <--
/dev/mapper/sda:
Magic : a92b4efc
Version : 00.90.03
UUID : 876ed759:74a31656:94332345:a976171b
Creation Time : Thu Feb 2 05:30:53 2006
Raid Level : raid5
Device Size : 244198464 (232.89 GiB 250.06 GB)
Array Size : 732595392 (698.66 GiB 750.18 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Wed Nov 29 03:12:12 2006
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Checksum : 7bd96cb9 - correct
Events : 0.9102893
Layout : left-symmetric
Chunk Size : 32K
Number Major Minor RaidDevice State
this 1 253 0 1 active sync /dev/mapper/sda
0 0 253 2 0 active sync /dev/mapper/sdc
1 1 253 0 1 active sync /dev/mapper/sda
2 2 253 1 2 active sync /dev/mapper/sdb
3 3 253 3 3 active sync /dev/mapper/sdd
/dev/mapper/sdb:
Magic : a92b4efc
Version : 00.90.03
UUID : 876ed759:74a31656:94332345:a976171b
Creation Time : Thu Feb 2 05:30:53 2006
Raid Level : raid5
Device Size : 244198464 (232.89 GiB 250.06 GB)
Array Size : 732595392 (698.66 GiB 750.18 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Tue Dec 5 04:31:06 2006
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 2
Spare Devices : 0
Checksum : 7be82e68 - correct
Events : 0.9324862
Layout : left-symmetric
Chunk Size : 32K
Number Major Minor RaidDevice State
this 2 253 1 2 active sync /dev/mapper/sdb
0 0 253 2 0 active sync /dev/mapper/sdc
1 1 0 0 1 faulty removed
2 2 253 1 2 active sync /dev/mapper/sdb
3 3 253 3 3 active sync /dev/mapper/sdd
/dev/mapper/sdc:
Magic : a92b4efc
Version : 00.90.03
UUID : 876ed759:74a31656:94332345:a976171b
Creation Time : Thu Feb 2 05:30:53 2006
Raid Level : raid5
Device Size : 244198464 (232.89 GiB 250.06 GB)
Array Size : 732595392 (698.66 GiB 750.18 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Tue Dec 5 04:45:20 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 4
Spare Devices : 0
Checksum : 7be831d7 - correct
Events : 0.9324869
Layout : left-symmetric
Chunk Size : 32K
Number Major Minor RaidDevice State
this 0 253 2 0 active sync /dev/mapper/sdc
0 0 253 2 0 active sync /dev/mapper/sdc
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 253 3 3 active sync /dev/mapper/sdd
/dev/mapper/sdd:
Magic : a92b4efc
Version : 00.90.03
UUID : 876ed759:74a31656:94332345:a976171b
Creation Time : Thu Feb 2 05:30:53 2006
Raid Level : raid5
Device Size : 244198464 (232.89 GiB 250.06 GB)
Array Size : 732595392 (698.66 GiB 750.18 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Tue Dec 5 04:45:20 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 4
Spare Devices : 0
Checksum : 7be831de - correct
Events : 0.9324869
Layout : left-symmetric
Chunk Size : 32K
Number Major Minor RaidDevice State
this 3 253 3 3 active sync /dev/mapper/sdd
0 0 253 2 0 active sync /dev/mapper/sdc
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 253 3 3 active sync /dev/mapper/sdd
--> please bite here <---> please bite here <---> please bite here <--
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^ permalink raw reply [flat|nested] 2+ messages in thread* Re: RAID5, 2 out of 4 disks failed, Events value differs too much
2006-12-05 8:48 RAID5, 2 out of 4 disks failed, Events value differs too much Bodo Thiesen
@ 2006-12-08 0:34 ` Corey Hickey
0 siblings, 0 replies; 2+ messages in thread
From: Corey Hickey @ 2006-12-08 0:34 UTC (permalink / raw)
Cc: linux-raid
Bodo Thiesen wrote:
> Hi, I have a little problem:
>
> Some hours ago the second of four disks were kicked out of my RAID5 thus rendering it unusable. As of my current knowledge, the disks are still working correctly (I assume a cable connection problem) but that's not the problem. The real problem is, that the first failed disk has an event value of 9102893, the second failed disk has a value of 9324862 and the other two disks have a value of 9324869. In this case, what is the best to do to recover the RAID? Because just recreating the array with the 9324862-disk and the two 9324869-disks and later hotadding the 9102893-disk, is just unclean and as I understood it, this would trigger some silent data failures. Is there a chance to prevent this data failures to happen at all, or is it at least possible to tell, where this error(s) are (so I can manually check the data and take appropriate steps)? Remember that I still have the data from th
e first failed disk, from which parts may still be relatively up to date.
>
> Has anyone had this problem already and found a nice solution for this?
If nobody gives you any better advice, I would follow this approach.
These commands are examples and may need to be fixed; I haven't had this
exact problem before (only similar ones) and I can't test anything right
now.
First, force the reassembly of the array using the three freshest disks.
# mdadm --assemble --force --run /dev/md0 /dev/sdb /dev/sdc /dev/sdd
Next, use whatever fsck program corresponds to your filesystem and do a
read-only check. Something like:
# reiserfsck --check /dev/md0
If fsck finds only a few problems, then it's probably safe to go ahead
and tell fsck to fix them; data loss will be minimal or nonexistent.
# reiserfsck --fix-fixable /dev/md0
Now you ought to be able to mount the filesystem and look around.
# mount /dev/md0
If all looks good, then hot-add the stale disk and let it resync.
# mdadm /dev/md0 -a /dev/sda
Good luck,
Corey
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