Red Hat Bugzilla – Bug 755409
cannot readd a partition to a mirror
Last modified: 2011-11-21 06:54:48 EST
/dev/sdb4 was a part of /dev/md2, but was removed manually. After reboot:
# cat /proc/mdstat
Personalities : [raid1]
md2 : active raid1 sda4
404468416 blocks [2/1] [_U]
# mdadm /dev/md2 -a /dev/sdb4
mdadm: /dev/sdb4 reports being an active member for /dev/md2, but a --re-add fails.
mdadm: not performing --add as that would convert /dev/sdb4 in to a spare.
mdadm: To make this a spare, use "mdadm --zero-superblock /dev/sdb4" first.
How do I readd sdb4 to md2?
Just follow the instructions provided in the output from mdadm.
The issue with raid1 is that if you just re-add it, mdadm wouldn't know
which of the two drives is authoritative and you could end up with old
If you mdadm --zero-superblock /dev/sdb4 first you should be able to re-add