echo check > /sys/block/md0/md/sync_action
watch -n 1 'cat /proc/mdstat'

1) Проверка raid1 массива. Например отказал /dev/sdb2

$sudo cat /proc/mdstat
Personalities : [raid0] [raid1] [raid5]
md1 : active raid1 sda2[0] sdb2[2](F)
918162880 blocks [2/1] [U_]
md2 : active raid1 sda3[0] sdb3[1]
19534976 blocks [2/1] [UU]
md0 : active raid1 sda1[0] sdb1[1]
39061952 blocks [2/1] [UU]

Для восстановления необходимо удалить поврежденный раздел, пометив его как сбойный, а потом его же добавить

$sudo mdadm /dev/md1 –f /dev/sdb2
$sudo mdadm /dev/md1 -r /dev/sdb2
$sudo mdadm /dev/md1 -a /dev/sdb2

После проверить статус raid1

$sudo cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md2 : active raid1 sda3[0] sdb3[1]
      19534976 blocks [2/2] [UU]

md1 : active raid1 sda2[2] sdb2[1]
      918162880 blocks [2/1] [_U]
      [=========>...........]  recovery = 45.7% (420430720/918162880) finish=80.9min speed=102490K/sec

md0 : active raid1 sda1[0] sdb1[1]
      39061952 blocks [2/2] [UU]

unused devices: <none>

Идет восстановление. После устранения проблемы, все md-разделы будут помечены [UU]

mdadm /dev/md0/ --re-add /dev/sdb1
mdadm /dev/md1/ --re-add /dev/sdb2
mdadm /dev/md2/ --re-add /dev/sda3
mdadm /dev/md3/ --re-add /dev/sdb5

echo resync > /sys/block/md0/md/sync_action
echo resync > /sys/block/md1/md/sync_action
echo resync > /sys/block/md2/md/sync_action
echo resync > /sys/block/md3/md/sync_action

cat /etc/fstab
mdadm --detail --scan
lsblk
lsscsi

# cat /etc/fstab
proc /proc proc defaults 0 0
none /dev/pts devpts gid=5,mode=620 0 0
/dev/md0 none swap sw 0 0
/dev/md1 /boot ext3 defaults 0 0
/dev/md2 / ext4 defaults 0 0
/dev/md3 /home ext4 defaults 0 0

# mdadm --detail --scan
ARRAY /dev/md/0 metadata=1.0 name=rescue:0 UUID=02d31d2c:95e07830:9facaa76:c2d67f3f
ARRAY /dev/md/1 metadata=1.0 name=rescue:1 UUID=81ae00c9:4eba9092:e125e8e9:e5dffe98
ARRAY /dev/md/2 metadata=1.0 name=rescue:2 UUID=ed40a0f2:d9a86d36:4dd86237:9a45d065
ARRAY /dev/md/3 metadata=1.0 name=rescue:3 UUID=fa674cf5:9a45d065:00ad11bc:12fae101

# lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE  MOUNTPOINT
sdb       8:16   0  2.7T  0 disk
├─sdb1    8:17   0   32G  0 part
├─sdb2    8:18   0  512M  0 part
├─sdb3    8:19   0    1T  0 part
│ └─md2   9:2    0 1024G  0 raid1 /
├─sdb4    8:20   0    1K  0 part
└─sdb5    8:21   0  1.7T  0 part
sda       8:0    0  2.7T  0 disk
├─sda1    8:1    0   32G  0 part
│ └─md0   9:0    0   32G  0 raid1 [SWAP]
├─sda2    8:2    0  512M  0 part
│ └─md1   9:1    0  512M  0 raid1 /boot
├─sda3    8:3    0    1T  0 part
├─sda4    8:4    0    1K  0 part
└─sda5    8:5    0  1.7T  0 part
  └─md3   9:3    0  1.7T  0 raid1 /home

# lsscsi
-bash: lsscsi: command not found

# mdadm --query --detail /dev/md2
/dev/md2:
        Version : 1.0
  Creation Time : Mon Mar 26 14:56:46 2012
     Raid Level : raid1
     Array Size : 1073741688 (1024.00 GiB 1099.51 GB)
  Used Dev Size : 1073741688 (1024.00 GiB 1099.51 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

    Update Time : Sun Feb  2 02:16:13 2014
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           Name : rescue:2
           UUID : ed40a0f2:d9a86d36:4dd86237:9a45d065
         Events : 991676

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       8       19        1      active sync   /dev/sdb3

# mdadm -a /dev/md2 /dev/sda3
mdadm: add new device failed for /dev/sda3 as 2: Invalid argument

# mdadm /dev/md2 --re-add /dev/sda3
mdadm: --re-add for /dev/sda3 to /dev/md2 is not possible[/cade] 

Personalities : [raid1]
md0 : active raid1 sda1[0]
      976760640 blocks super 1.0 [2/1] [U_]
      bitmap: 6/8 pages [24KB], 65536KB chunk

unused devices: <none>