mdadm --examine /dev/sd[abcd]1
/dev/sda1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 86c1bc11:9d641e12:851311c4:3d33aa63
           Name : ubuntu:0  (local to host ubuntu)
  Creation Time : Wed May 25 15:59:11 2016
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 3906764976 (1862.89 GiB 2000.26 GB)
     Array Size : 5860147200 (5588.67 GiB 6000.79 GB)
  Used Dev Size : 3906764800 (1862.89 GiB 2000.26 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262056 sectors, after=176 sectors
          State : clean
    Device UUID : 2712f137:41b6060c:7de24bf4:80c726e4

Internal Bitmap : 8 sectors from superblock
    Update Time : Wed May 25 15:59:11 2016
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : 3030874b - correct
         Events : 0

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 0
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdb1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 86c1bc11:9d641e12:851311c4:3d33aa63
           Name : ubuntu:0  (local to host ubuntu)
  Creation Time : Wed May 25 15:59:11 2016
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 3906764976 (1862.89 GiB 2000.26 GB)
     Array Size : 5860147200 (5588.67 GiB 6000.79 GB)
  Used Dev Size : 3906764800 (1862.89 GiB 2000.26 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262056 sectors, after=176 sectors
          State : clean
    Device UUID : b5489f5c:4d047675:f65d39ea:7e8f4322

Internal Bitmap : 8 sectors from superblock
    Update Time : Wed May 25 15:59:11 2016
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : f2584f5c - correct
         Events : 0

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 1
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdc1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 86c1bc11:9d641e12:851311c4:3d33aa63
           Name : ubuntu:0  (local to host ubuntu)
  Creation Time : Wed May 25 15:59:11 2016
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 3906764800 (1862.89 GiB 2000.26 GB)
     Array Size : 5860147200 (5588.67 GiB 6000.79 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262056 sectors, after=0 sectors
          State : clean
    Device UUID : 7e99ecd0:6357befc:c138c0a4:351213db

Internal Bitmap : 8 sectors from superblock
    Update Time : Wed May 25 15:59:11 2016
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : 61445010 - correct
         Events : 0

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 2
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdd1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 86c1bc11:9d641e12:851311c4:3d33aa63
           Name : ubuntu:0  (local to host ubuntu)
  Creation Time : Wed May 25 15:59:11 2016
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 3906764800 (1862.89 GiB 2000.26 GB)
     Array Size : 5860147200 (5588.67 GiB 6000.79 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262056 sectors, after=0 sectors
          State : clean
    Device UUID : a7aa4acc:5b5b664f:983b2e34:edd38261

Internal Bitmap : 8 sectors from superblock
    Update Time : Wed May 25 15:59:11 2016
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : c52829bf - correct
         Events : 0

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 3
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
root@ubuntu:~#

root@ubuntu:~# !190
sudo mdadm -D /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Wed May 25 15:59:11 2016
     Raid Level : raid5
     Array Size : 5860147200 (5588.67 GiB 6000.79 GB)
  Used Dev Size : 1953382400 (1862.89 GiB 2000.26 GB)
   Raid Devices : 4
  Total Devices : 4
    Persistence : Superblock is persistent

  Intent Bitmap : Internal

    Update Time : Wed May 25 15:59:11 2016
          State : clean
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

           Name : ubuntu:0  (local to host ubuntu)
           UUID : 86c1bc11:9d641e12:851311c4:3d33aa63
         Events : 0

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1
       2       8       33        2      active sync   /dev/sdc1
       3       8       49        3      active sync   /dev/sdd1
root@ubuntu:~#