fdisk -l
=============================================
WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sda: 3000.5 GB, 3000592982016 bytes
255 heads, 63 sectors/track, 364801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x03afffbe

Device Boot Start End Blocks Id System
/dev/sda1 1 267350 2147483647+ ee EFI GPT

WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sdb: 3000.5 GB, 3000592982016 bytes
255 heads, 63 sectors/track, 364801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x142a889c

Device Boot Start End Blocks Id System
/dev/sdb1 1 267350 2147483647+ ee EFI GPT

WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sdc: 3000.5 GB, 3000592982016 bytes
255 heads, 63 sectors/track, 364801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x3daebd50

Device Boot Start End Blocks Id System
/dev/sdc1 1 267350 2147483647+ ee EFI GPT

Disk /dev/md0: 21.4 GB, 21484339200 bytes
2 heads, 4 sectors/track, 5245200 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk identifier: 0x00000000

Disk /dev/md0 doesn't contain a valid partition table

mdadm --examine /dev/sd[abcd]1
=============================================
/dev/sda1:
Magic : a92b4efc
Version : 00.90.00
UUID : 7d247a6e:7b5d46c8:f52d9c89:db304b21
Creation Time : Mon Apr 23 19:55:36 2012
Raid Level : raid1
Used Dev Size : 20980800 (20.01 GiB 21.48 GB)
Array Size : 20980800 (20.01 GiB 21.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 0

Update Time : Mon Jun 27 21:12:23 2016
      State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 1a57db60 - correct
Events : 164275

  Number   Major   Minor   RaidDevice State
this 0 8 1 0 active sync /dev/sda1

0 0 8 1 0 active sync /dev/sda1
1 1 8 17 1 active sync /dev/sdb1
2 2 0 0 2 faulty removed
3 3 8 33 3 active sync /dev/sdc1
/dev/sdb1:
Magic : a92b4efc
Version : 00.90.00
UUID : 7d247a6e:7b5d46c8:f52d9c89:db304b21
Creation Time : Mon Apr 23 19:55:36 2012
Raid Level : raid1
Used Dev Size : 20980800 (20.01 GiB 21.48 GB)
Array Size : 20980800 (20.01 GiB 21.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 0

Update Time : Mon Jun 27 21:12:23 2016
      State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 1a57db72 - correct
Events : 164275

  Number   Major   Minor   RaidDevice State
this 1 8 17 1 active sync /dev/sdb1

0 0 8 1 0 active sync /dev/sda1
1 1 8 17 1 active sync /dev/sdb1
2 2 0 0 2 faulty removed
3 3 8 33 3 active sync /dev/sdc1
/dev/sdc1:
Magic : a92b4efc
Version : 00.90.00
UUID : 7d247a6e:7b5d46c8:f52d9c89:db304b21
Creation Time : Mon Apr 23 19:55:36 2012
Raid Level : raid1
Used Dev Size : 20980800 (20.01 GiB 21.48 GB)
Array Size : 20980800 (20.01 GiB 21.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 0

Update Time : Mon Jun 27 21:12:23 2016
      State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 1a57db86 - correct
Events : 164275

  Number   Major   Minor   RaidDevice State
this 3 8 33 3 active sync /dev/sdc1

0 0 8 1 0 active sync /dev/sda1
1 1 8 17 1 active sync /dev/sdb1
2 2 0 0 2 faulty removed
3 3 8 33 3 active sync /dev/sdc1
=============================================