root@openmediavault:~# cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [ra                              id10]
md0 : active raid1 sda[0]
      3906887488 blocks super 1.2 [2/1] [U_]
      bitmap: 26/30 pages [104KB], 65536KB chunk

root@openmediavault:~# blkid
/dev/sdb1: UUID="67f8957f-4256-43ef-a546-498710a572b3" TYPE="ext4" PARTUUID="951c56cc-01"
/dev/sdb5: UUID="e9fbcafa-57d3-4b1f-84fd-3817730f2d34" TYPE="swap" PARTUUID="951c56cc-05"
/dev/sda: UUID="1ac92da3-fccb-cadf-9c4a-9dc00083c1ca" UUID_SUB="1ba3b553-71cb-9121-72d4-7f7d9d4095d9" LABEL="o          penmediavault:0" TYPE="linux_raid_member"
/dev/md0: LABEL="RAID" UUID="012310dd-0a1d-4e68-bf83-079109e5f9ec" TYPE="ext4"
/dev/sdd: UUID="1ac92da3-fccb-cadf-9c4a-9dc00083c1ca" UUID_SUB="5c462bbe-2613-4aa3-9102-cb1917d7df2d" LABEL="o          penmediavault:0" TYPE="linux_raid_member"
/dev/sdc1: UUID="8A58FCA958FC9563" TYPE="ntfs" PARTUUID="95cc0009-01"

root@openmediavault:~# fdisk -l | grep "Disk "
Disk /dev/sdb: 74.5 GiB, 80000000000 bytes, 156250000 sectors
Disk model: ST3808110AS
Disk identifier: 0x951c56cc
Disk /dev/sda: 3.7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk model: HITACHI HUS72404
Disk /dev/sdd: 3.7 TiB, 4000787030016 bytes, 7814037168 sectors
Disk model: HITACHI HUS72404
Disk /dev/md0: 3.7 TiB, 4000652787712 bytes, 7813774976 sectors
Disk /dev/sdc: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Disk model: 418AS  External
Disk identifier: 0x95cc0009

root@openmediavault:~# cat /etc/mdadm/mdadm.conf
# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
# Note, if no DEVICE line is present, then "DEVICE partitions" is assumed.
# To avoid the auto-assembly of RAID devices a pattern that CAN'T match is
# used if no RAID devices are configured.
DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# definitions of existing MD arrays
ARRAY /dev/md0 metadata=1.2 name=openmediavault:0 UUID=1ac92da3:fccbcadf:9c4a9dc0:0083c1ca
MAILADDR root

root@openmediavault:~# mdadm --detail --scan --verbose
ARRAY /dev/md0 level=raid1 num-devices=2 metadata=1.2 name=openmediavault:0 UUID=1ac92da3:fccbcadf:9c4a9dc0:0083c1ca
   devices=/dev/sda

2- HITACHI 0F14683 Ultrastar A7K4000 4TB 7200 RPM 64MB cache SATA 6.0Gb/s 3.5 internal hard drive