I inherited a Scientific Linux 6.2 system that had a triple mirror for it's OS device; sda, sdb, & sdc. I tried to remove sdc from the mirror using:
<pre>
mdadm --fail /dev/md0 /dev/sdc1
mdadm --remove /dev/md0 /dev/sdc1
</pre>
but the device md0 shows degraded:
<pre>
# mdadm --detail /dev/md0
/dev/md0:
Version : 1.0
Creation Time : Fri Jul 20 07:38:36 2012
Raid Level : raid1
Array Size : 511988 (500.07 MiB 524.28 MB)
Used Dev Size : 511988 (500.07 MiB 524.28 MB)
Raid Devices : 3
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Tue Aug 28 16:25:57 2012
State : clean, degraded
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Name : localhost.localdomain:0
UUID : 8b68d22d:4566147a:621a50a4:6d016578
Events : 325
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
3 8 17 1 active sync /dev/sdb1
2 0 0 2 removed
#
</pre>
I did the same thing with md1 and it too is in the same state.
mdadm.conf looks like this:
<pre>
# mdadm.conf written out by anaconda
MAILADDR root
AUTO
imsm 1.x -all
ARRAY /dev/md0 metadata=1.0 level=raid1 num-devices=2 UUID=8b68d22d:4566147a:621a50a4:6d016578
ARRAY /dev/md1 metadata=1.1 level=raid1 num-devices=2 UUID=b2bc5b0b:4d3a33ba:39e6a2fb:be3ae14c
</pre>
Is there any way to clear up the degraded state of these MD devices? I tried zero-superblock but it didn't work:
<pre>
# mdadm --zero-superblock /dev/sdc
mdadm: Unrecognised md component device - /dev/sdc
# mdadm --zero-superblock /dev/sdc1
mdadm: Unrecognised md component device - /dev/sdc1
#
</pre>