Problem with auto-assembling raid1 on system start

[Tobias Gunkel <tobias.gunkel@qumido.de>]

Hello everyone!

After rebooting one of our Debian servers yesterday (under normal 
conditions), mdadm was not able to assemble /dev/md0 automaticly any more.
System: Debian Lenny, mdmadm v2.5.6, Kernel 2.6.26-preemptive-cpuset 
(from Debian testing sources)

This is what I get during boot:

   [...]
   Begin: Mounting root file system... ...
   Begin: Running /scripts/local-top ...
   Begin: Loading MD modules ...
   md: raid1 personality registered for level 1
   Success: loaded module raid1.
   Done.
   Begin: Assembling all MD arrays ...
   [...]
   md: md0 stopped.
   mdadm: no devices found for /dev/md0
   Failure: failed to assemble all arrays.
   [...]

Then the system falls back to BusyBox shell from initramfs, because the 
root fs  - which is located on /dev/md0 - could not be mounted.
But from the initramfs shell, it is possible to cleanly assemble and 
mount the md0 array:

   (initramfs) mdadm -A /dev/md0 /dev/sda2 /dev/sdb2
   md: md0 stopped.
   md: bind<sdb2>
   md: bind<sda2>
   raid1: raid set md0 active with 2 out of 2 mirrors
   mdadm: /dev/md0 has been started with 2 drives.

   (initramfs) mount /dev/md0 root
   kjournald starting. Commit interval 5 seconds
   EXT3 FS on md0, internal journal
   EXT3-fs: mounted filesystem with ordered data mode.

After leaving the initramfs shell with 'exit', the system continues to 
boot normally.

Strange: /dev/md1 (swap) which is the first array in assembling order, 
gets assembled and started correctly.
I also played around with ROOTDELAY=60, but this did not changed anything.

I'm grateful for any help.
Best regards, Tobias


PS: Maybe some helpful output (after starting the system the way 
described above):

$ cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda2[0] sdb2[1]
      487331648 blocks [2/2] [UU]

md1 : active raid1 sda1[0] sdb1[1]
      1052160 blocks [2/2] [UU]

unused devices: <none>


$ mdadm --detail --scan
ARRAY /dev/md1 level=raid1 num-devices=2 
UUID=c3838888:50dbed72:15a9bffb:d0e83d23
ARRAY /dev/md0 level=raid1 num-devices=2 
UUID=0d0a0c79:70adae03:f802952b:2b58c14d


$ grep -v ^# /etc/mdadm/mdadm.conf

DEVICE /dev/sd*[0-9] /dev/sd*[0-9]

CREATE owner=root group=disk mode=0660 auto=yes

HOMEHOST <system>

MAILADDR root

ARRAY /dev/md1 level=raid1 num-devices=2 
UUID=c3838888:50dbed72:15a9bffb:d0e83d23
ARRAY /dev/md0 level=raid1 num-devices=2 
UUID=0d0a0c79:70adae03:f802952b:2b58c14d


$ mdadm --detail /dev/md0
/dev/md0:
        Version : 00.90.03
  Creation Time : Thu Dec 11 14:18:44 2008
     Raid Level : raid1
     Array Size : 487331648 (464.76 GiB 499.03 GB)
    Device Size : 487331648 (464.76 GiB 499.03 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Fri May  8 15:45:32 2009
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           UUID : 0d0a0c79:70adae03:f802952b:2b58c14d
         Events : 0.900

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2