mdXX: bitmap superblock UUID mismatch

[Reynald Borer <reynald.borer@gmail.com>]

Hello guys,

I have been using md raids for quite a long time now and it always
worked fine, until recently when I upgraded some hardware on my
workstation. Unfortunately the hardware I changed proved itself to be
very unstable, and I encountered a lot of hard lockups of the system
while running. Those lockups recently made one of my raid 1 array
fails with the infamous error message "mdXX: bitmap superblock UUID
mismatch".

Here is what I have found in the kernel logs when I try to activate
the given raid group:
-----------------
md/raid1:md126: active with 2 out of 2 mirrors
md126: bitmap superblock UUID mismatch
md126: bitmap file superblock:
         magic: 6d746962
       version: 4
          uuid: 37102258.af9c1930.b8397fb8.eba356af
        events: 199168
events cleared: 199166
         state: 00000000
     chunksize: 524288 B
  daemon sleep: 5s
     sync size: 248075584 KB
max write behind: 0
md126: failed to create bitmap (-22)
-----------------


Such error messages are displayed each time I try to run the raid
group. Content of /proc/mdstat is:
-----------------
md126 : inactive sdb6[0] sda6[1]
      496151168 blocks
-----------------


If I try to examine both disks with mdadm -E it shows some checksum
mismatch for both partitions:
-----------------
root@bob # mdadm -E /dev/sda6
/dev/sda6:
          Magic : a92b4efc
        Version : 0.90.03
           UUID : 37102258:bf9c1930:b8397fb8:eba356af
  Creation Time : Mon Aug  7 21:06:47 2006
     Raid Level : raid1
  Used Dev Size : 248075584 (236.58 GiB 254.03 GB)
     Array Size : 248075584 (236.58 GiB 254.03 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 6

    Update Time : Wed Jan 12 00:12:44 2011
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : e4883f8e - expected e4883e8e
         Events : 199168


      Number   Major   Minor   RaidDevice State
this     1       8       38        1      active sync

   0     0       8       70        0      active sync
   1     1       8       38        1      active sync
root@bob # mdadm -E /dev/sdb6
/dev/sdb6:
          Magic : a92b4efc
        Version : 0.90.03
           UUID : 37102258:bf9c1930:b8397fb8:eba356af
  Creation Time : Mon Aug  7 21:06:47 2006
     Raid Level : raid1
  Used Dev Size : 248075584 (236.58 GiB 254.03 GB)
     Array Size : 248075584 (236.58 GiB 254.03 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 6

    Update Time : Wed Jan 12 00:12:44 2011
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : e4883fac - expected e4883eac
         Events : 199168


      Number   Major   Minor   RaidDevice State
this     0       8       70        0      active sync

   0     0       8       70        0      active sync
   1     1       8       38        1      active sync
-----------------


Any idea how I could try to save my raid group?

Thanks in advance for your help.

Best Regards,
Reynald