root@ubuntu:/# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdc3[1]
      2921734976 blocks super 1.2 [2/1] [_U]

unused devices: <none>


root@ubuntu:/# mdadm --detail --scan
ARRAY /dev/md/0 metadata=1.2 name=lager:0 UUID=da7e00d9:09fe00a5:0f2e0157:b0b13381


root@ubuntu:/# mdadm -D /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Wed Feb 26 16:26:34 2014
     Raid Level : raid1
     Array Size : 2921734976 (2786.38 GiB 2991.86 GB)
  Used Dev Size : 2921734976 (2786.38 GiB 2991.86 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

    Update Time : Fri Oct  3 15:04:23 2014
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           Name : lager:0  (local to host lager)
           UUID : da7e00d9:09fe00a5:0f2e0157:b0b13381
         Events : 6329863

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       8       35        1      active sync   /dev/sdc3

root@ubuntu:/# df -h
Filesystem           Size  Used Avail Use% Mounted on
/dev/md0             2.7T  300G  2.3T  12% /
udev                 3.9G  4.0K  3.9G   1% /dev
tmpfs                1.6G  328K  1.6G   1% /run
none                 5.0M     0  5.0M   0% /run/lock
none                 3.9G     0  3.9G   0% /run/shm

root@ubuntu:/# cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/md127 during installation
UUID=baf6a940-e5dc-4f41-902e-b817e828727b /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda3 during installation
UUID=ee93ca04-4da0-408d-b99f-6e85955a247f none            swap    sw              0       0
# swap was on /dev/sdb2 during installation
UUID=9249175b-7c3f-4a60-bedb-7bf9e3b0d893 none            swap    sw              0       0
/dev/sda1 /home/meganerd/backup ext4 rw 0 0

root@ubuntu:/# sudo blkid
/dev/sda1: UUID="b9dca62c-9303-4ad5-b5d1-e1c54e268d48" TYPE="ext4"
/dev/sdb2: UUID="da7e00d9-09fe-00a5-0f2e-0157b0b13381" UUID_SUB="150654f5-f991-077c-585d-34962d76e91f" LABEL="lager:0" TYPE="linux_raid_member"
/dev/sdb3: UUID="ee93ca04-4da0-408d-b99f-6e85955a247f" TYPE="swap"
/dev/sdc2: UUID="9249175b-7c3f-4a60-bedb-7bf9e3b0d893" TYPE="swap"
/dev/sdc3: UUID="da7e00d9-09fe-00a5-0f2e-0157b0b13381" UUID_SUB="f608953f-5ddb-923c-cc3d-f8d7f6d59348" LABEL="lager:0" TYPE="linux_raid_member"
/dev/md0: UUID="baf6a940-e5dc-4f41-902e-b817e828727b" TYPE="ext4"