We have a number of Xen virtual machines that use disk image files.
disk = ["file:/xen/vbd/something.vbd,sda1,w"]
We'd like to use DRBD to replicate these files for backup (as opposed to the mess of MySQL replication and nightly rsyncs we have at the moment). But I don't seem to understand how to make it work.
We can bind a file to a loopback device with
# losetup /dev/loop0 /xen/vbd/something.vbd
And point DRBD to that device:
device /dev/drbd1; disk /dev/loop0;
But the loopback isn't stable - it isn't there on reboot, and could easily have been attached to loop1, loop2 etc. It isn't exactly a valid option for a server if it needs human interaction to recover with a power interruption.
What am I missing?