Comment 6 for bug 791454

It would appear that the swap mirror re-starts OK; the ext4 filesystem mirrors do not - might be related:

ubuntu@ubuntu:/var/log$ cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 vda2[0] vdb2[1]
      314356 blocks super 1.2 [2/2] [UU]

md2 : active raid1 vda3[0]
      315380 blocks super 1.2 [2/1] [U_]

md0 : active raid1 vda1[0]
      1464308 blocks super 1.2 [2/1] [U_]

unused devices: <none>
ubuntu@ubuntu:/var/log$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md0 1.4G 889M 448M 67% /
none 238M 216K 237M 1% /dev
none 247M 0 247M 0% /dev/shm
none 247M 44K 247M 1% /var/run
none 247M 0 247M 0% /var/lock
/dev/md2 299M 11M 273M 4% /home
ubuntu@ubuntu:/var/log$