How do I get mdadm to auto assemble my raid array?

Question

After upgrading to Ubuntu 9.04, my raid 5 array is no longer being assembled correctly. Right now, from boot, it will start a raid array using ata-MAXTOR_STM3500630AS_9QG03T0L-part1, at /dev/md0, but that is fail because it isn't my whole Raid 5 setup. This was working fine in 8.10.

I've tried tweaking the following config. I figured mdadm would follow my config on boot but it seems to have a mind of its own.

If I stop /dev/md0 and then restart /dev/md1 it will sometimes cleanly start. Otherwise I have to re-add ata-MAXTOR_STM3500630AS_9QG03T0L-part1 to the array and it starts a 300 minute recovery.

Tried:

• Setting array to "/dev/md0"
• Using the straight /dev/sd[bcde] in DEVICE and ARRAY config file.

How can I get Ubuntu and mdadm to start /dev/md1 cleanly on boot again?

My /etc/mdadm/mdadm.conf:

MAILADDR [email protected]
DEVICE /dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG03T0L-part1 /dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG07KQW-part1 /dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG07KZB-part1 /dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG07N72-part1 /dev/sdb1
ARRAY /dev/md1 level=raid5 devices=/dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG03T0L-part1,/dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG07KQW-part1,/dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG07KZB-part1,/dev/disk/by-id/ata-MAXTOR_STM3500630AS_9QG07N72-part1,/dev/sdb1

mdadm --misc --detail /dev/md1:

/dev/md1:
        Version : 00.90
  Creation Time : Sun Aug 12 20:28:18 2007
     Raid Level : raid5
     Array Size : 1465151808 (1397.28 GiB 1500.32 GB)
  Used Dev Size : 488383936 (465.76 GiB 500.11 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 1
    Persistence : Superblock is persistent

    Update Time : Tue Jul 21 23:07:44 2009
          State : clean, degraded, recovering
 Active Devices : 3
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 4K

 Rebuild Status : 14% complete

           UUID : 0223d5de:73491d5e:a219b166:4fedadc6
         Events : 0.7040

    Number   Major   Minor   RaidDevice State
       0       8       49        0      active sync   /dev/sdd1
       1       8       65        1      active sync   /dev/sde1
       4       8       17        2      spare rebuilding   /dev/sdb1
       3       8       33        3      active sync   /dev/sdc1

Would specifying the UUID in the mdadm.conf work to help get mdadm started on boot?

Thanks for your help!

Solution 1

Using the UUID is the preferred method. Also see what /usr/share/mdadm/mkconf outputs and try using that.

You are updating the initramfs after you change /etc/mdadm/mdadm.conf right? If you don't, when you boot your changes won't be used. update-initramfs -u should do it.

Solution 2

In MY experience mdadm does not respect device-by-id names in mdadm.conf and just plain fails to rebuild the array.

If you replace device-by-id with /dev/sdXn controller references it should work fine.

BA

Comments

[Asik]

Fixed finally. Had to run `mdadm --assemble /dev/md0 --update=homehost. Then I used the modified my mdadm.conf to use 'DEVICE partitions' and pointed the ARRAY line to the new uuid of the array. Things magically work now

[Asik]

I've tried setting the UUID as the device in the ARRAY of my mdadm.conf and rebuilding using update-initramfs -u but that hasn't helped. It seems like one of the superblocks might be confusing mdadm since it will continue to load /dev/md1 with a separate subset of the drives. Running sudo mdadm --stop /dev/md1 and then sudo mdadm --assemble /dev/md1 is required to get things going after a boot.