I have a RAID5 with 8 disks. It worked fine.
I made an update from ubuntu 10.04 to 12.04 using do-release-upgrade,
and rebooted.
before: kernel 2.6.32-41, mdadm v2.6.7.1, after: kernel 3.2.0-41, mdadm
3.2.5 - and I made a copy of the root partition before I updated, so I
can still boot both OSs
After I rebooted, one drive dropped from the array. I don't know why: it
was fine hardware-wise, and the same happened with my other RAID5 array,
where the dropped drive was fine, too. This seems like an MD or Ubuntu
bug to me.
So, I readded it and resynced. When the resync was around or over 80%
done, another harddrive failed (maybe because the resync is now using
all sectors the first time since a long time), this one with a real
hardware failure, so I had to permanently removed it. Now, the first
drive, which was dropped although it was fine, is marked as spare,
although it should have mostly good data on it. mdadm refuses to re-add
it, no matter what I try. mdadm 3.2.5 says "not possible" (see [1]),
while mdadm 2.5.7.1 re-adds it, but as spare, not as real member, so the
array still won't restart.
I need to forcibly re-add the drive that's marked as spare, because it
should have good data on it. I understand that some blocks may be out of
sync or corrupted, but the array has many TB and I want to get to the
rest of all the data that's still good. Even if I get 80% recovered,
that's still better than 0%.
NB 1:
Please do NOT respond with
* restore backup - the backup doesn't have the new data, which I
really need
* re-"create" the array - unless you can give me the exact --create
command that would recover it with data - other people tried this
based on suggestions in forums and they lost all data
Appendix 1:
dmesg during resync:
...
[45345.341865] XFS (dm-13): xfs_imap_to_bp: xfs_trans_read_buf()
returned error 5.
[45345.341909] XFS (dm-13): metadata I/O error: block 0x45986fc0
("xfs_trans_read_buf") error 5 buf count 8192
(many times, about the same handful of blocks)
[45345.610858] XFS (dm-13): metadata I/O error: block 0x7a434f20
("xfs_trans_read_buf") error 5 buf count 4096
(many times, about the same handful of blocks)
(And then probably MD shut down the disk, and the RAID, and so all the
other filesystems went in the trash, too:)
[45353.184049] XFS (dm-10): xfs_log_force: error 5 returned.
[45472.694283] XFS (dm-8): metadata I/O error: block 0x29e89be8
("xfs_trans_read_buf") error 5 buf count 4096
[45473.504044] XFS (dm-10): xfs_log_force: error 5 returned.
[45485.246757] XFS (dm-8): metadata I/O error: block 0x19010c29
("xlog_iodone") error 5 buf count 2560
[45485.248966] XFS (dm-8): xfs_do_force_shutdown(0x2) called from line
1007 of file /build/buildd/linux-3.2.0/fs/xfs/xfs_log.c. Return address
= 0xffffffffa031ede1
[45485.249011] XFS (dm-8): Log I/O Error Detected. Shutting down filesystem
[45485.251126] XFS (dm-8): Please umount the filesystem and rectify the
problem(s)
[45503.584037] XFS (dm-10): xfs_log_force: error 5 returned.
[45514.848040] XFS (dm-8): xfs_log_force: error 5 returned.
Appendix 2:
1. During resync, i.e. after sdl was wrongly dropped, and before sdk failed:
# cat /proc/mdstat
md0 : active raid5 sdl[8] sdp[5] sdq[7] sdk[1] sdj[0] sdo[4] sdn[6] sdm[3]
6837337472 blocks level 5, 64k chunk, algorithm 2 [8/7] [UU_UUUUU]
[>....................] recovery = 0.1% (1075328/976762496)
finish=468.6min speed=34700K/sec
# mdadm --detail /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Raid Devices : 8
Total Devices : 8
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Thu Apr 11 16:59:55 2013
State : clean, degraded, recovering
Active Devices : 7
Working Devices : 8
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
Rebuild Status : 0% complete
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Events : 0.13240512
Number Major Minor RaidDevice State
0 8 144 0 active sync /dev/sdj
1 8 160 1 active sync /dev/sdk
8 8 176 2 spare rebuilding /dev/sdl
3 8 192 3 active sync /dev/sdm
4 8 224 4 active sync /dev/sdo
5 8 240 5 active sync /dev/sdp
6 8 208 6 active sync /dev/sdn
7 65 0 7 active sync /dev/sdq
2. after sdk had a hardware fault during resync:
after resync, towards the end (between 78 and 100%), again:
md0 : active raid5 sdj[0] sdl[8](S) sdq[7] sdn[6] sdp[5] sdo[4] sdm[3]
sdk[9](F)
6837337472 blocks level 5, 64k chunk, algorithm 2 [8/6] [U__UUUUU]
*-disk:1
description: ATA Disk
product: WDC WD10EACS-00D
vendor: Western Digital
physical id: 0.1.0
bus info: scsi@7:0.1.0
logical name: /dev/sdk
version: 1A01
serial: WD-...8520
size: 931GiB (1TB)
capacity: 931GiB (1TB)
capabilities: 15000rpm
configuration: ansiversion=5
*-disk:2
description: ATA Disk
product: WDC WD10EACS-00D
vendor: Western Digital
physical id: 0.2.0
bus info: scsi@7:0.2.0
logical name: /dev/sdl
version: 1A01
serial: WD-WCAU45964913
size: 931GiB (1TB)
capacity: 931GiB (1TB)
capabilities: 15000rpm
configuration: ansiversion=5
3. Current state, after fix attempts:
(sdk has hardware failure
sdl is probably good, but marked spare)
# cat /proc/mdstat
md0 : inactive sdk[9](S) sdl[8](S) sdj[0] sdq[7] sdn[6] sdp[5] sdo[4] sdm[3]
7814099968 blocks
# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Raid Devices : 8
Total Devices : 8
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Fri Apr 12 17:09:30 2013
State : active, degraded, Not Started
Active Devices : 6
Working Devices : 8
Failed Devices : 0
Spare Devices : 2
Layout : left-symmetric
Chunk Size : 64K
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Events : 0.13274865
Number Major Minor RaidDevice State
0 8 144 0 active sync /dev/sdj
1 0 0 1 removed
2 0 0 2 removed
3 8 192 3 active sync /dev/sdm
4 8 224 4 active sync /dev/sdo
5 8 240 5 active sync /dev/sdp
6 8 208 6 active sync /dev/sdn
7 65 0 7 active sync /dev/sdq
8 8 176 - spare /dev/sdl
9 8 160 - spare /dev/sdk
# mdadm -E /dev/sd[jlmnopqk]
(sdl is the one I need to add:)
/dev/sdl:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 7
Preferred Minor : 0
Update Time : Fri Apr 12 15:00:38 2013
State : clean
Active Devices : 6
Working Devices : 7
Failed Devices : 2
Spare Devices : 1
Checksum : ca6e81a9 - correct
Events : 13274863
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 8 8 176 8 spare /dev/sdl
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
8 8 8 176 8 spare /dev/sdl
/dev/sdj:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : clean
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a40ffb - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 0 8 144 0 active sync /dev/sdj
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
/dev/sdm:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : active
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a41030 - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 3 8 192 3 active sync /dev/sdm
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
/dev/sdn:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : active
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a41046 - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 6 8 208 6 active sync /dev/sdn
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
/dev/sdo:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : active
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a41052 - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 4 8 224 4 active sync /dev/sdo
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
/dev/sdp:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : active
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a41064 - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 5 8 240 5 active sync /dev/sdp
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
/dev/sdq:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : active
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a40fb1 - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 7 65 0 7 active sync /dev/sdq
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
(sdk with serial ...8520 had the hardware fault:)
/dev/sdk:
Magic : a92b4efc
Version : 00.90.00
UUID : c71c4168:de3a9b44:5ac2d0d1:4a2cd41c
Creation Time : Sun Mar 22 15:51:17 2009
Raid Level : raid5
Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
Array Size : 6837337472 (6520.59 GiB 7001.43 GB)
Raid Devices : 8
Total Devices : 6
Preferred Minor : 0
Update Time : Fri Apr 12 17:09:30 2013
State : clean
Active Devices : 6
Working Devices : 6
Failed Devices : 2
Spare Devices : 0
Checksum : c9a410bf - correct
Events : 13274865
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 9 8 160 -1 spare /dev/sdk
0 0 8 144 0 active sync /dev/sdj
1 1 0 0 1 faulty removed
2 2 0 0 2 faulty removed
3 3 8 192 3 active sync /dev/sdm
4 4 8 224 4 active sync /dev/sdo
5 5 8 240 5 active sync /dev/sdp
6 6 8 208 6 active sync /dev/sdn
7 7 65 0 7 active sync /dev/sdq
NB 2:
The original problem is that md dropped a perfectly good drive from the
array, just because I upgraded the OS. It seems to me that Linux MD is
all too happy and quick to kick out drives from the array, and then
refuses to readd them without a resync. This might be fine approach on
paper, but not in reality, where the resync is probably when another
drive fails, and then you have no parity left and you're told that your
data is gone.
1. It shouldn't drop drives so quickly
2. It should allow me to re-add them, if I think the data is good
3. There must be a recovery mechanism, to at least partially recover
data. Arrays can easily have 10+ TB, and just because a few
blocks/sectors in one filesystem are bad doesn't mean that I need to
throw away all filesystems that are on that LVM, and all data in the
broken filesystem.
NB 3: Seems like other people have the exact same problem:
http://www.linuxquestions.org/questions/linux-server-73/mdadm-re-added-disk-treated-as-spare-750739/
http://forums.gentoo.org/viewtopic-t-716757.html
https://raid.wiki.kernel.org/index.php/RAID_Recovery#Recreating_an_array
NB 4: Last time I upgraded the OS on the RAID server, I ended up with a
similar mess, due to another md bug:
https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/136252 )
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