You can't do an restfs with the new btrfs-progs.
Posted: Sat Jul 27, 2013 7:07 am
There is a change in the btrfs-progs-0.20_rc1_p358. If you want to create an filesystem on an already formated device, you had ta add the parameter -f (force) to the mkfs.btrfs command. Without this you can't use fsarchiver with btrfs.