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.