Hi Neil,
I recently came across what I believe is a regression in mdadm, which
has been introduced in version 3.1.3.
It seems that, when using metadata 1.x, the handling of failed/detached
drives isn't effective anymore.
Here's a quick example:
[root@GrosCinq ~]# mdadm -C /dev/md4 -l1 -n2 --metadata=1.0 /dev/sdc1
/dev/sdd1
mdadm: array /dev/md4 started.
[root@GrosCinq ~]#
[root@GrosCinq ~]# mdadm --wait /dev/md4
[root@GrosCinq ~]#
[root@GrosCinq ~]# mdadm -D /dev/md4
/dev/md4:
Version : 1.0
Creation Time : Thu Feb 10 13:56:31 2011
Raid Level : raid1
Array Size : 1953096 (1907.64 MiB 1999.97 MB)
Used Dev Size : 1953096 (1907.64 MiB 1999.97 MB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Thu Feb 10 13:56:46 2011
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Name : GrosCinq:4 (local to host GrosCinq)
UUID : bbfef508:252e7ce1:c95d4a03:8beb3cbd
Events : 17
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sdc1
1 8 49 1 active sync /dev/sdd1
[root@GrosCinq ~]# mdadm --fail /dev/md4 /dev/sdc1
mdadm: set /dev/sdc1 faulty in /dev/md4
[root@GrosCinq ~]#
[root@GrosCinq ~]# mdadm -D /dev/md4 | tail -n 6
Number Major Minor RaidDevice State
0 0 0 0 removed
1 8 49 1 active sync /dev/sdd1
0 8 1 - faulty spare /dev/sdc1
[root@GrosCinq ~]#
[root@GrosCinq ~]# mdadm --remove /dev/md4 failed
[root@GrosCinq ~]#
[root@GrosCinq ~]# mdadm -D /dev/md4 | tail -n 6
Number Major Minor RaidDevice State
0 0 0 0 removed
1 8 49 1 active sync /dev/sdd1
0 8 1 - faulty spare /dev/sdc1
[root@GrosCinq ~]#
This is with mdadm 3.1.4, 3.1.3 or even 3.2, but not 3.1.2. I did a git
bisect to try and isolate the regression and it appears the guilty
commit is :
b3b4e8a : "Avoid skipping devices where removing all faulty/detached
devices."
As stated in the commit, this is only true with metadata 1.x. With 0.9,
there is no problem. I also tested with detached drives as well as
raid5/6 and encountered the same issue. Actually, with detached drives,
it's even more annoying, since using --remove detached is the only way
to remove the device without restarting the array. For a failed drive,
there is still the possibility to use the device name.
Do you have any idea of the reason behind that regression ? Shall this
patch only apply in the case of 0.9 metadata ?
Regards,
--
Rémi
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