Creation
Warning
Only use partitions, never whole devices, otherwise assembly will fail after reboot!
RAID 0
mdadm --create /dev/md0 --level=0 \
--raid-devices=2 /dev/sd[bc]1
RAID 1
mdadm --create /dev/md0 --level=1 \
--raid-devices=2 /dev/sd[bc]1
RAID 5
mdadm --create /dev/md0 --level=5 \
--raid-devices=3 /dev/sd[b-d]1