md/raid1 fails to detect on boot

[jeff at bubble.org]

> I have two RAID1 drives with multiple partitions.
>
> Each time I reboot, one of the partitions comes up degraded with only one
> of
> the two devices. The only thing that the kernel logs is:
>
> [   13.327731] md/raid1:md3: active with 1 out of 2 mirrors
>
> I can hot-add the other partition, and wait for mdadm to resync it, but on
> the next reboot it's degraded again. This is getting old.
>
> I note that both drives have md0 through md3. There are no defects on
> either
> drive. And it's always md3 that fails to be assembled fully, when the
> kernel
> boots.

Can you check the following

1) what does /etc/mdadm.conf say for /dev/md3? it should have a line like:

ARRAY /dev/md3 level=raid1 num-devices=2
UUID=1bcb5496:c7d158e6:14c0bbc3:de3ed72e

2) what does "blkid | grep sd[ab]x" say? (x is the partition number) both
should have the same UUID number:

/dev/sdb3: UUID="1bcb5496-c7d1-58e6-14c0-bbc3de3ed72e"
TYPE="linux_raid_member"
/dev/sda3: UUID="1bcb5496-c7d1-58e6-14c0-bbc3de3ed72e"
TYPE="linux_raid_member"

3) what does /etc/fstab show for your boot (root?) partition? should be:
UUID=61a11dc6-b7b7-4fb0-893c-83ce87be9324 /          ext4    defaults     
  1 1

4) what does "blkid | grep md3" show? should be like:
/dev/md3: UUID="61a11dc6-b7b7-4fb0-893c-83ce87be9324" TYPE="ext4"




notice the UUID's match for items 1 & 2, they also match for 3 & 4

mdadm.conf says build the array out of the partitions with the devices
with UUID 1bcb5496:c7d158e6:14c0bbc3:de3ed72e, which in my example are
/dev/sda3 and /dev/sdb3

Line 3 says that the / (root) partition is on UUID device
61a11dc6-b7b7-4fb0-893c-83ce87be9324 this UUID is the RAID device UUID,
make sure it is not pointing to the UUID of the disk.

line 4 shows the UUID for the md3 partition.

Hopefully its this simple and not something else going on.
Jeff