(All of this is running as root btw, so using sudo)

mdadm -A --run /dev/md1 /dev/sdb1
mkdir /mnt/sdb1
mount -r /dev/md1 /dev/sdb1

mdadm -A --run /dev/md2 /dev/sdb2
mkdir /mnt/sdb2
mount -r /dev/md2 /dev/sdb2