I have a fresh install of Debian 7.4 (Kernel 3.2.54-2) formatted as btrfs for testing in a VM before implementing this at home. I am using the 1.3.2-1 Debian package from the stable branch. I see in the Administration manual that you are supposed to do this to test btrfs:
mkdir /etc/urbackup
echo "/etc/urbackup/backupfolder" > /etc/urbackup/backupfolder
You can then test if UrBackup will use the btrfs features via
urbackup_snapshot_helper test
echo $?
When I do this, I get a “1” as the return code. Does this mean UrBackup is not detecting a valid btrfs configuration or can’t do cross-device reflinks? What do I need to do to make this work? My final configuration will most likely be a small VM disk formatted as EXT4, then a larger drive formatted as btrfs mounted to “/media/BACKUP/urbackup”.
Am I also correct in that when this is working, I will only see the benefits during the file backups and not the image backups?
It says in the same section that you need at least kernel 3.6 for the cross device reflinks. That is probably the problem. You can get a newer kernel via debian backports. I’d switch to the most recent one, as btrfs gets improved continously and improvements are not backported to older kernels. I’ll add some more output the “test” call.
Yup, switching to Ubuntu 13.10 took care of the issue. I see that only file backups are able to take advantage of the btrfs, even between full file backups. All image backups consume their normal amount of space. I’m going to wait and do my golden install next month after Ubuntu 14.04LTS comes out.