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I have a 64bit Ubuntu Jaunty server (kernel 2.6.28-17-server) installed on two SATA disks (sdc and sde) in a mirror RAID, this being my current raid configuration:

cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]

md5 : active raid1 sdd7[1] sdc7[0]
      126953536 blocks [2/2] [UU]

md2 : active raid1 sdd3[1] sdc3[0]
      979840 blocks [2/2] [UU]

md0 : active raid1 sdd1[1] sdc1[0]
      96256 blocks [2/2] [UU]

md4 : active raid1 sdd6[1] sdc6[0]
      9767424 blocks [2/2] [UU]

md3 : active raid1 sdd5[1] sdc5[0]
      979840 blocks [2/2] [UU]

md1 : active raid1 sdd2[1] sdc2[0]
      1951808 blocks [2/2] [UU]

unused devices: none
# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md4              9.2G  922M  7.9G  11% /
tmpfs                 490M     0  490M   0% /lib/init/rw
varrun                490M  316K  490M   1% /var/run
varlock               490M     0  490M   0% /var/lock
udev                  490M  228K  490M   1% /dev
tmpfs                 490M     0  490M   0% /dev/shm
lrm                   490M  2.5M  488M   1% /lib/modules/2.6.28-17-server/volatile
/dev/md0               89M   55M   30M  65% /boot
/dev/md5              120G   96G   18G  85% /data
/dev/md2              942M   18M  877M   2% /tmp
/dev/md3              942M  186M  709M  21% /var

Users are quickly filling up the /data Samba share, so I added two additional hard disks (sda and sdb, they are the exact same type and size), as I wanted to create another mirror out of them and then mounted the new raid device inside /data.

Steps I took was creating one Linux raid autodetect partition on each of the new disks, making sure that they are the same size.

 fdisk /dev/sda -l

Disk /dev/sda: 122.9 GB, 122942324736 bytes
255 heads, 63 sectors/track, 14946 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000e2e78

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1       14946   120053713+  fd  Linux raid autodetect
fdisk /dev/sdb -l

Disk /dev/sdb: 122.9 GB, 122942324736 bytes
255 heads, 63 sectors/track, 14946 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000ef08e

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       14946   120053713+  fd  Linux raid autodetect

Next I created the new mirror:

mdadm --create /dev/md6 --level=mirror --raid-devices=2 /dev/sda1 /dev/sdb1
At which point I got the following warning:
mdadm: /dev/sdb1 appears to contain an ext2fs file system
    size=120053712K  mtime=Sat Dec 19 11:10:30 2009
Continue creating array?

This is weird, as I just created the new partition, and I never had a filesystem created on it, but anyway, I continued on and waited for the sync to finish.

Everything seems fine:

cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md6 : active raid1 sdb1[1] sda1[0]
      120053632 blocks [2/2] [UU]

md5 : active raid1 sdd7[1] sdc7[0]
      126953536 blocks [2/2] [UU]

md2 : active raid1 sdd3[1] sdc3[0]
      979840 blocks [2/2] [UU]

md4 : active raid1 sdc6[0] sdd6[1]
      9767424 blocks [2/2] [UU]

md3 : active raid1 sdc5[0] sdd5[1]
      979840 blocks [2/2] [UU]

md1 : active raid1 sdc2[0] sdd2[1]
      1951808 blocks [2/2] [UU]

md0 : active raid1 sdc1[0] sdd1[1]
      96256 blocks [2/2] [UU]

unused devices: none
mdadm --detail /dev/md6
/dev/md6:
        Version : 00.90
  Creation Time : Sat Dec 19 11:33:31 2009
     Raid Level : raid1
     Array Size : 120053632 (114.49 GiB 122.93 GB)
  Used Dev Size : 120053632 (114.49 GiB 122.93 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 6
    Persistence : Superblock is persistent

    Update Time : Sat Dec 19 12:24:14 2009
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           UUID : b901925f:b5ca90e0:afcf3cfb:09b88def (local to host szerver.mtvsz.local)
         Events : 0.4

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1

But once I reboot, here comes the problem:

cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md_d6 : inactive sdb1[1](S)
      120053632 blocks

md3 : active raid1 sdc5[0] sdd5[1]
      979840 blocks [2/2] [UU]

md5 : active raid1 sdc7[0] sdd7[1]
      126953536 blocks [2/2] [UU]

md2 : active raid1 sdc3[0] sdd3[1]
      979840 blocks [2/2] [UU]

md1 : active raid1 sdd2[1] sdc2[0]
      1951808 blocks [2/2] [UU]

md0 : active raid1 sdd1[1] sdc1[0]
      96256 blocks [2/2] [UU]

md4 : active raid1 sdd6[1] sdc6[0]
      9767424 blocks [2/2] [UU]

unused devices: none
 ls /dev/md*
/dev/md0  /dev/md2  /dev/md4  /dev/md_d6    /dev/md_d6p2  /dev/md_d6p4
/dev/md1  /dev/md3  /dev/md5  /dev/md_d6p1  /dev/md_d6p3

So my question is: What the hell is this with md_d6 and its partitions?

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1 Answer 1

Ok, it seems this is a mdadm bug or I missed a manual step. After issuing this command

mdadm --examine --scan --config=mdadm.conf >> /etc/mdadm/mdadm.conf

and rebooting it seems the raid array is now ok. Stupid bug :)

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