1. Find the devices associated with the RAID device

mdadm --detail <raid_device>

The last lines of output of the above command shows the associated devices (see the example below).

2. Deactivate the RAID device

mdadm --stop <raid_device>

3. Remove the RAID itself

mdadm --remove <raid_device>

4. remove the superblocks on all devices that were associated with the RAID device

mdadm --zero-superblock  [component_device2 ...]

EXAMPLE

Let’s assume we want to remove ‘/dev/md0’:

# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Mon Jun 30 20:12:38 2014
     Raid Level : raid1
     Array Size : 104791936 (99.94 GiB 107.31 GB)
  Used Dev Size : 104791936 (99.94 GiB 107.31 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Tue Jul  1 08:45:19 2014
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : asma:0  (local to host asma)
           UUID : f6aa0270:b923c624:ad30ceff:db9964b4
         Events : 613

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       2       8       17        1      active sync   /dev/sdb1

# mdadm --stop /dev/md0
mdadm: stopped /dev/md0
# mdadm --remove /dev/md0
# mdadm --zero-superblock /dev/sda1 /dev/sdb1