I just use plain rsync and then do a btrfs snapshot each time. Very fast and easy to set up. Probably just as easy with zfs if you prefer that.

Of course I've got some setup around creating datestamped snapshots and keeping the N last ( http://sprunge.us/OKHb?bash for the bash function that does this), but in essence it's just

$ rsync src trg/current $ btrfs subvolume snapshot -r trg/current trg/snapshot-$(date)