I have
absolutely no dog in this fight at all but, in case anyone is interested, if you don't have zfs on a system you can create and maintain "rsync snapshots" by using hard links that take up zero space:
http://www.mikerubel.org/computers/rsync_snapshots/
The idea is, you rsync to a snapshot directory (just like .zfs/snapshot/name_of_snapshot would be) but since you are hardlinking everything, almost all of the files take up zero space. Only files that change get their hardlinks broken and take up any space.
You can put the dir names in rotation and make them work exactly like zfs snapshots.
This is how people did snapshots before zfs.