Hi,
The RAID5 I set up originally had 2 PATA drives and 2 SATA drives. I
recently purchased 2 more SATA drives, so I wanted to swap out the PATA ones
one at a time. In my infinite wisdom I did the following:
1. Shutdown.
2. Physically removed the PATA drive (/dev/hdb, with partition /dev/hdb5).
3. Installed the SATA drive.
4. Booted up; saw a message that a device had failed but there were no
spares to rebuild.
5. Partitioned the new drive.
6. mdadm --add /dev/md5 /dev/sdc5 (added the new drive).
As you can see, the new SATA drive was added as /dev/sdc. My reasoning for
removing hdb5 outright rather than marking it failed was that I hoped it
would be easier to reinsert hdb5 and rebuild the array if something bad
happened (say, if sda failed) while the array was rebuilding.
Since RAID5 works as you would expect, it rebuilt md5 without any problems
as soon as I added /dev/sdc5 to the RAID. However, if I type this command:
mdadm --detail /dev/md5
...I see the following output (note Total Devices: 5 and Failed Devices:1):
-------------------------------------------------------------------------------------------------
/dev/md5:
Version : 00.90.00
Creation Time : Mon Sep 5 16:47:04 2005
Raid Level : raid5
Array Size : 146512320 (139.73 GiB 150.03 GB)
Device Size : 48837440 (46.58 GiB 50.01 GB)
Raid Devices : 4
Total Devices : 5
Preferred Minor : 5
Persistence : Superblock is persistent
Update Time : Tue Mar 7 01:30:33 2006
State : dirty, no-errors
Active Devices : 4
Working Devices : 4
Failed Devices : 1
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
1 8 21 1 active sync /dev/sdb5
2 8 37 2 active sync /dev/sdc5
3 22 69 3 active sync /dev/hdd5
UUID : 811eb962:7ab90bd2:585e740e:fe7a507b
Events : 0.42
-------------------------------------------------------------------------------------------------
Everything seems to be happy and functioning, but it's really bugging me
that I can't get rid of the failed device. At first I thought it was
because my /etc/mdadm.conf was out-of-date. However, I replaced instances
of /dev/hdb* with /dev/sdc* in the /etc/mdadm.conf.
I noticed someone else has also had this problem but didn't have a solution
(scroll to the very bottom):
http://www.digitalmapping.sk.ca/Networks/ExpandingRAID.htm
Doing mdadm --remove /dev/md5 /dev/hdb5 won't work any more, because
/dev/hdb5 doesn't exist any more, and even if it did, by now I would
consider hdb invalid or corrupt because new data has been written to the
RAID.
So, friends, how do you suggest I get rid of that faulty device so I can
clear my conscience?
-Rob
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