Check RAID status:
/sbin/mdadm --detail /dev/md0
Or check with this:
sudo cat /proc/mdstat
This is what a good status will look like:
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sdb5[0] sdc5[1]
1485888 blocks [2/2] [UU]
md0 : active raid1 sdb1[0] sdc1[1]
242709888 blocks [2/2] [UU]
unused devices:
The [UU] (I think) indicates the status of both drives in the array, and both are Up