CentOS 6.3
2.6.32-279.19.1
mdadm-3.2.3-9.el6.x86_64
I have noticed that the device number printed in the mdstat file gets
changed if you fail->remove->add a member device of a 1.X metadata
array, but for a 0.90 metadata array the device will go back to the
original value once recovery has finished.
This means after recovery has finished I end up with the following
outputs for 1.1 and 0.90 metadata:
1.1 METADATA /proc/mdstat (trimmed)
md50 : active raid1 loop0[2] loop1[1]
32760 blocks super 1.1 [2/2] [UU]
1.1 METADATA mdadm --detail (trimmed)
Number Major Minor RaidDevice State
2 7 0 0 active sync /dev/loop0
1 7 1 1 active sync /dev/loop1
0.90 METADATA /proc/mdstat (trimmed)
md50 : active raid1 loop0[0] loop1[1]
32704 blocks [2/2] [UU]
0.90 METADATA mdadm --detail (trimmed)
Number Major Minor RaidDevice State
0 7 0 0 active sync /dev/loop0
1 7 1 1 active sync /dev/loop1
Is this by design? I know 1.X version of metadata use dev_roles rather
than this_disk and the mdp_disk_t structure so maybe it is by design?
A simple re-creator is below if you want to see it in action Please
analyze it first to make sure my assumptions are valid in your case.
Change --meta from 1.1 to 0.90 to see it for the other metadata.
# Create two sparse disk image files
dd if=/dev/zero of=/tmp/disk1.img bs=1 count=0 seek=32M
dd if=/dev/zero of=/tmp/disk2.img bs=1 count=0 seek=32M
# Set them up as loopback devices
losetup -f /tmp/disk1.img
losetup -f /tmp/disk2.img
# Create a raid 1 out of them
mdadm --create /dev/md50 --level=1 --raid-devices=2 --meta=1.1
/dev/loop0 /dev/loop1
# Fail/remove/zero-superblock/add device back to array
mdadm --fail /dev/md50 /dev/loop0
sleep 1
mdadm --remove /dev/md50 /dev/loop0
sleep 1
mdadm --zero-superblock /dev/loop0
sleep 1
mdadm --add /dev/md50 /dev/loop0
cat /proc/mdstat | grep -A 2 md50
sleep 10
cat /proc/mdstat | grep -A 2 md50
# Clean up
mdadm --stop /dev/md50
losetup -d /dev/loop0
losetup -d /dev/loop1
rm -f /tmp/disk1.img
rm -f /tmp/disk2.img
Thanks for any input!
Dusty
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