[mythtv-users] linux software raid / mdadm UUID problems
drescherjm at gmail.com
Thu Dec 31 12:47:17 UTC 2009
> I upgraded the motherboard in my storage system today, and reinstalled
> Ubuntu 9.10. There are 2 Linux software raid arrays in the system,
> /dev/md0 which is comprised of 8 devices, and /dev/md1 which is
> comprised of 2 devices. I can get mdadm to automatically assemble
> /dev/md1 on boot, but it won't auto assemble /dev/md0. For some reason
> (possibly because I had a 4 disk array with some of the same disks
> years ago), mdadm finds two instances of /dev/md0. One is correctly
> comprised of /dev/sd[abcdefgh]1, the other is incorrectly comprised of
> /dev/sd[bc] and two missing devices:
> mike at storage1:~$ sudo mdadm --examine --scan --verbose
> ARRAY /dev/md0 level=raid5 num-devices=4
> ARRAY /dev/md1 level=raid1 num-devices=2
> ARRAY /dev/md0 level=raid5 num-devices=8
> spares=1 devices=/dev/sdh1,/dev/sdg1,/dev/sdf1,/dev/sde1,/dev/sdd1,/dev/sdc1,/dev/sdb1,/dev/sda1
> I'm not sure why these mis-marked partitions weren't a problem for me before.
> When I use fdisk to look for partitions marked as Linux raid, I see
> exactly what I would expect:
> mike at storage1:~$ sudo fdisk -l |grep auto
> /dev/sda1 * 1 36481 293033601 fd Linux raid autodetect
> /dev/sda3 36743 38913 17438557+ fd Linux raid autodetect
> /dev/sdb1 * 1 36481 293033601 fd Linux raid autodetect
> /dev/sdc1 * 1 36481 293033601 fd Linux raid autodetect
> /dev/sdd1 1 36481 293033601 fd Linux raid autodetect
> /dev/sde1 * 1 36481 293033601 fd Linux raid autodetect
> /dev/sde3 36743 38913 17438557+ fd Linux raid autodetect
> /dev/sdf1 * 1 36481 293033601 fd Linux raid autodetect
> /dev/sdg1 * 1 36481 293033601 fd Linux raid autodetect
> /dev/sdh1 1 36481 293033601 fd Linux raid autodetect
> Note that sd[ae]3 are part of /dev/md1
> I can manually start the array with:
> sudo mdadm --assemble --uuid=afdf5b45:8b930e27:66ac6d52:07eb4ce7
> /dev/md0 , so I know the array is intact.
How about cat /proc/mdstat?
> How do I get rid of the erroneous /dev/md0? It looks like I may be
> able to use the --zero-superblock option on /dev/sd[bc], but I value
> the data on the array, and am wary of doing anything that could
> jeopardize the data on /dev/sd[bc]1.
At work and home I manage dozens of mdadm arrays over the last 5 to 7
years and I have never had to zero a superblock. I have moved entire
arrays from machine to machine, replaced individual drives,
controllers and grown arrays.
Did you edit your /etc/mdadm.conf? Do you even have one?
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