First, stop using the old raid tools. Use mdadm only! mdadm would not have
allowed your error to occur.
If you start the array with n-1 disk, it can't re-build.
I think you can recover. I simulated your mistake. See results:
Status of array before I started to trash it:
Number Major Minor RaidDevice State
0 1 1 0 active sync /dev/ram1
1 1 14 1 active sync /dev/ram14
2 1 13 2 active sync /dev/ram13
3 1 0 3 active sync /dev/ram0
Failed 1 disk:
# mdadm /dev/md3 -f /dev/ram14
mdadm: set /dev/ram14 faulty in /dev/md3
Attempt to remove another disk, but mdadm will not allow:
# mdadm /dev/md3 -r /dev/ram13
mdadm: hot remove failed for /dev/ram13: Device or resource busy
Fail another disk, the array is now in a vary bad state:
# mdadm /dev/md3 -f /dev/ram13
mdadm: set /dev/ram13 faulty in /dev/md3
Remove the second failed disk:
# mdadm /dev/md3 -r /dev/ram13
mdadm: hot removed /dev/ram13
Now I attempt to recover.
Stop the array:
# mdadm -S /dev/md3
Check the status:
# mdadm -D /dev/md3
mdadm: md device /dev/md3 does not appear to be active.
Now start the array, listing n-1 disks.
# mdadm --assemble --force /dev/md3 /dev/ram0 /dev/ram1 /dev/ram13
mdadm: forcing event count in /dev/ram13(2) from 66 upto 69
mdadm: clearing FAULTY flag for device 2 in /dev/md3 for /dev/ram13
mdadm: /dev/md3 has been started with 3 drives.
Add the disk that failed first:
# mdadm /dev/md3 -a /dev/ram14
mdadm: hot added /dev/ram14
After a re-sync the array is fine.
So, at this point, this is what you need to do:
Stop the array:
mdadm -S /dev/mdx
Start the array using the 4 good disks, not the disk that failed first.
mdadm --assemble --force <list the 4 good disks>
Your array should be up at this point.
You can now add the failed disk:
mdadm /dev/mdx -a /dev/xxx
Hope this helps!
If you have questions, just post again.
Guy
-----Original Message-----
From: linux-raid-owner@xxxxxxxxxxxxxxx
[mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Robert Osiel
Sent: Friday, November 12, 2004 10:35 PM
To: linux-raid@xxxxxxxxxxxxxxx
Subject: A few mdadm questions
Hello.
I have a five-disk RAID 5 array in which one disk's failure went
unnoticed for an indeterminate time. Once I finally noticed, I did a
raidhotremove on the disk -- or what I thought was the disk.
Unfortunately, I can't count. Now my array has one 'failed' disk and
one 'spare' disk. Aaargh.
Since then, I've learned a lot, but I haven't been able to find
reassurances and/or answers elsewhere on a few issues.
The two big questions are:
1) How can I mark the 'spare' disk as 'clean' and get it back in the
array? If I read the mdadm source correctly, it looks like 'removed'
disks are skipped when trying to assemble.
2) If I --assemble --force the array and just specify (n-1) disks, does
that ensure that (if the array starts) it starts in degraded mode and
won't start re-writing the parity information?
Thanks a bunch in advance for any help.
Bob
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
