I'm setting up a mdadm raid 1 array on Ubuntu 14.10 under VirtualBox. Everything works fine:
The raid 1 is set up with /dev/sdc1 and /dev/sdd1:
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdd1[2] sdc1[0]
1045952 blocks super 1.2 [2/2] [UU]
unused devices: <none>
However, if I unplug one of the disks, say /dev/sdb, here's what I get:
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : inactive sdc1[2](S)
1046016 blocks super 1.2
unused devices: <none>
This is not what I expected... I was expecting a degraded Raid 1 array, not an inactive array. What am I doing wrong?
My mdadm.conf lists the array as:
# definitions of existing MD arrays
ARRAY /dev/md/0 level=raid1 num-devices=2 devices=/dev/sdc1,/dev/sdd1 metadata=1.2 UUID=ffa72d1e:a18e2f76:2d336ad8:5f01069b name=ubuntu:0