What can one make of this output? Note the change once I ran mdchk.
[root@juhfah ~]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb2[1]
6289344 blocks [2/1] [_U]
md3 : active raid1 sda3[2](F) sdb3[1]
4192896 blocks [2/1] [_U]
md5 : active raid1 sdb5[1] sda5[0]
1052160 blocks [2/2] [UU]
md2 : active raid1 sda2[2](F) sdb6[1]
1052160 blocks [2/1] [_U]
md4 : active raid1 sdb7[1]
231504576 blocks [2/1] [_U]
md0 : active raid1 sdb1[1] sda1[0]
104320 blocks [2/2] [UU]
unused devices: <none>
[root (at mark) juhfah ~]# /etc/rc.d/init.d/mdchk
-- Reading system configuration from /etc/raidtab
/dev/md0 [raid1]: <sda1> <sdb1>
/dev/md1 [raid1]: <sda2> <sdb2>
/dev/md2 [raid1]: <sda6> <sdb6>
/dev/md3 [raid1]: <sda3> <sdb3>
/dev/md4 [raid1]: <sda7> <sdb7>
/dev/md5 [raid1]: <sda5> <sdb5>
-- Reading current status from /proc/mdstat
/dev/md0 [raid1]: <sdb1> <sda1> (ACTIVE)
! /dev/md1 [raid1]: <sdb2> (FAIL)
! /dev/md2 [raid1]: <sda2> <sdb6> (FAIL)
! /dev/md3 [raid1]: <sda3> <sdb3> (FAIL)
! /dev/md4 [raid1]: <sdb7> (FAIL)
/dev/md5 [raid1]: <sdb5> <sda5> (ACTIVE)
-- Writing MBR(s) accorind to /proc/mdstat
-- Failed RAID device(s): /dev/sda2 /dev/sda6 /dev/sda7
-- Fixing failed partition: /dev/sda2
-- Fixing failed partition: /dev/sda3
-- Adding missing partition: /dev/sda2
/dev/md2: can not hot-add disk: invalid argument.
-- Adding missing partition: /dev/sda6
/dev/md6: can not hot-add disk: array not running!
-- Adding missing partition: /dev/sda7
/dev/md7: can not hot-add disk: array not running!
-- RAID status: OK
[root@juhfah ~]#
[root@juhfah ~]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb2[1]
6289344 blocks [2/1] [_U]
md3 : active raid1 sda3[0] sdb3[1]
4192896 blocks [2/2] [UU]
md5 : active raid1 sdb5[1] sda5[0]
1052160 blocks [2/2] [UU]
md2 : active raid1 sda2[0] sdb6[1]
1052160 blocks [2/2] [UU]
md4 : active raid1 sdb7[1]
231504576 blocks [2/1] [_U]
md0 : active raid1 sdb1[1] sda1[0]
104320 blocks [2/2] [UU]
unused devices: <none>
[root (at mark) juhfah ~]# /etc/rc.d/init.d/mdchk
-- Reading system configuration from /etc/raidtab
/dev/md0 [raid1]: <sda1> <sdb1>
/dev/md1 [raid1]: <sda2> <sdb2>
/dev/md2 [raid1]: <sda6> <sdb6>
/dev/md3 [raid1]: <sda3> <sdb3>
/dev/md4 [raid1]: <sda7> <sdb7>
/dev/md5 [raid1]: <sda5> <sdb5>
-- Reading current status from /proc/mdstat
/dev/md0 [raid1]: <sdb1> <sda1> (ACTIVE)
! /dev/md1 [raid1]: <sdb2> (FAIL)
/dev/md2 [raid1]: <sda2> <sdb6> (ACTIVE)
/dev/md3 [raid1]: <sda3> <sdb3> (ACTIVE)
! /dev/md4 [raid1]: <sdb7> (FAIL)
/dev/md5 [raid1]: <sdb5> <sda5> (ACTIVE)
-- Writing MBR(s) accorind to /proc/mdstat
-- Failed RAID device(s): /dev/sda2 /dev/sda6 /dev/sda7
-- Adding missing partition: /dev/sda2
/dev/md2: can not hot-add disk: invalid argument.
-- Adding missing partition: /dev/sda6
/dev/md6: can not hot-add disk: array not running!
-- Adding missing partition: /dev/sda7
/dev/md7: can not hot-add disk: array not running!
-- RAID status: OK
[root@juhfah ~]#
[root@juhfah ~]#
[root (at mark) juhfah ~]# /etc/rc.d/init.d/mdchk
-- Reading system configuration from /etc/raidtab
/dev/md0 [raid1]: <sda1> <sdb1>
/dev/md1 [raid1]: <sda2> <sdb2>
/dev/md2 [raid1]: <sda6> <sdb6>
/dev/md3 [raid1]: <sda3> <sdb3>
/dev/md4 [raid1]: <sda7> <sdb7>
/dev/md5 [raid1]: <sda5> <sdb5>
-- Reading current status from /proc/mdstat
/dev/md0 [raid1]: <sdb1> <sda1> (ACTIVE)
! /dev/md1 [raid1]: <sdb2> (FAIL)
/dev/md2 [raid1]: <sda2> <sdb6> (ACTIVE)
/dev/md3 [raid1]: <sda3> <sdb3> (ACTIVE)
! /dev/md4 [raid1]: <sdb7> (FAIL)
/dev/md5 [raid1]: <sdb5> <sda5> (ACTIVE)
-- Writing MBR(s) accorind to /proc/mdstat
-- Failed RAID device(s): /dev/sda2 /dev/sda6 /dev/sda7
-- Adding missing partition: /dev/sda2
/dev/md2: can not hot-add disk: invalid argument.
-- Adding missing partition: /dev/sda6
/dev/md6: can not hot-add disk: array not running!
-- Adding missing partition: /dev/sda7
/dev/md7: can not hot-add disk: array not running!
-- RAID status: OK