Saturday, March 1, 2014

Mdadm External Write-intent Bitmap Hack (Debian update)

I recently upgraded to Debian 7.4 and found that I needed to redo my external write intent bitmap hack. My old methods no longer worked.

First I needed to disable mdadm assembly when running from the ramdisk. Edit /etc/default/mdadm and set the following:

Rebuild the ramdisk image with:
update-initramfs -u

You still need to prevent mdadm from assembling the array listed in /etc/mdadm/mdadm.conf so that
DEVICE /dev/null

I created a new mdadm config file names /etc/mdadm/mdadm.delayed.conf which is a copy of /etc/mdadm/mdadm.conf but leaving
DEVICE partitions
as is. I also specify the bitmap file on the ARRAY definition line
ARRAY /dev/md/127 metadata=0.90 bitmap=/md127-raid5-bitmap UUID=....

Next I created a new script /etc/init.d/delayedRaid
#!/bin/sh # # Start all arrays specified in the delayed configuration file. # # Copyright © 2014 Joshua Allen # Distributable under the terms of the GNU GPL version 2. # ### BEGIN INIT INFO # Provides: delayedRaid # Required-Start: $local_fs mdadm-raid # Should-Start: # X-Start-Before: # Required-Stop: # Should-Stop: $local_fs mdadm-raid # X-Stop-After: # Default-Start: S # Default-Stop: 0 6 # Short-Description: Delayed MD array assembly # Description: This script assembles delayes assembly of MD raid # devices. Useful for raid devices that use external # write intent bitmaps. # Settings are in /etc/mdadm/mdadm.delayed.conf ### END INIT INFO . /lib/lsb/init-functions do_start() { log_action_begin_msg "Starting delayed raid" mdadm --assemble --scan --config=/etc/mdadm/mdadm.delayed.conf log_action_end_msg $? mount /mnt/raid5 } do_stop() { umount /mnt/raid5 mdadm --stop --scan --config=/etc/mdadm/mdadm.delayed.conf } case "$1" in start) do_start ;; restart|reload|force-reload) echo "Error: argument '$1' not supported" >&2 exit 3 ;; stop) # No-op do_stop ;; *) echo "Usage: delayedRaid [start|stop]" >&2 exit 3 ;; esac

And I added to the start-up procedures with
insserv -d delayedRaid

After reboot check to see if
Intent Bitmap : {some file name}
is present when running
mdadm --detail /your/raid/device

Hopefully I didn't miss anything.

No comments:

Post a Comment