Bug#422554: After reboot, drives marked faulty/removed get reassebled as the mirrored array instead of the healthy ones

[Binzberger Viktor]

Package: mdadm
Version: 2.5.6-9

I don't know whether this is a bug, but here's what happened.
I had two mirrors operational /dev/hd[ac]1 and /dev/hd[ac]3 on md0 and md1, respectively.
On Apr 23, /dev/hdc started to complain about bad sectors. I first marked it as faulty, 
and then removed it from the array with mdadm. I didn't have physical access to the machine, 
so I didn't remove /dev/hdc. On Apr 27, the owner of the machine rebooted the machine with ssh -> "reboot"

It is just now that I've discovered that ever since the reboot, mdadm reassembled the bad hdc[13]
partitions as md?, instead of using the healthy hda[13]!

Here is what I see now:

cat /proc/mdstat:

Personalities : [raid1]
md1 : active raid1 hdc3[1]
      29294400 blocks [2/1] [_U]

md0 : active raid1 hdc1[0]
      4883648 blocks [2/1] [U_]

unused devices: <none>

mdadm -D /dev/md0

/dev/md0:
        Version : 00.90.03
  Creation Time : Tue Jan  1 00:49:59 2002
     Raid Level : raid1
     Array Size : 4883648 (4.66 GiB 5.00 GB)
    Device Size : 4883648 (4.66 GiB 5.00 GB)
   Raid Devices : 2
  Total Devices : 1
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sun May  6 23:19:41 2007
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           UUID : 712b8608:01ac77cf:8ac60fa3:f9a08b86
         Events : 0.160454

    Number   Major   Minor   RaidDevice State
       0      22        1        0      active sync   /dev/hdc1
       1       0        0        1      removed


mdadm --examine /dev/hda1
/dev/hda1:
          Magic : a92b4efc
        Version : 00.90.01
           UUID : 712b8608:01ac77cf:8ac60fa3:f9a08b86
  Creation Time : Tue Jan  1 00:49:59 2002
     Raid Level : raid1
    Device Size : 4883648 (4.66 GiB 5.00 GB)
     Array Size : 4883648 (4.66 GiB 5.00 GB)
   Raid Devices : 1
  Total Devices : 1
Preferred Minor : 0

    Update Time : Fri Apr 27 20:58:51 2007
          State : clean
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 2319a8de - correct
         Events : 0.64780


      Number   Major   Minor   RaidDevice State
this     0       3        1        0      active sync   /dev/hda1

   0     0       3        1        0      active sync   /dev/hda1


mdadm --examine /dev/hdc1

/dev/hdc1:
          Magic : a92b4efc
        Version : 00.90.01
           UUID : 712b8608:01ac77cf:8ac60fa3:f9a08b86
  Creation Time : Tue Jan  1 00:49:59 2002
     Raid Level : raid1
    Device Size : 4883648 (4.66 GiB 5.00 GB)
     Array Size : 4883648 (4.66 GiB 5.00 GB)
   Raid Devices : 2
  Total Devices : 1
Preferred Minor : 0

    Update Time : Sun May  6 22:33:38 2007
          State : clean
 Active Devices : 1
Working Devices : 1
 Failed Devices : 1
  Spare Devices : 0
       Checksum : 232883dc - correct
         Events : 0.159894


      Number   Major   Minor   RaidDevice State
this     0      22        1        0      active sync   /dev/hdc1

   0     0      22        1        0      active sync   /dev/hdc1
   1     1       0        0        1      faulty removed


Is this thing OK? I don't have the opportunity to experiment with this machine, and I had to fix it in the meanwhile, so 
I cannot give you further debug information on the issue.

Cheers, 
Viktor