cat /proc/mdstat

root@velocity-MS-7740:~# cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sdb2[1] sda2[2]
      483625984 blocks super 1.2 [2/2] [UU]
      bitmap: 0/4 pages [0KB], 65536KB chunk

md3 : active raid1 sdb4[1] sda4[2]
      487196672 blocks super 1.2 [2/2] [UU]
      bitmap: 0/4 pages [0KB], 65536KB chunk

md2 : active raid1 sdb3[1] sda3[2]
      4100096 blocks super 1.2 [2/2] [UU]

md0 : active raid1 sdb1[1] sda1[2]
      1023424 blocks super 1.2 [2/2] [UU]

unused devices: <none>