Comment 18 for bug 876146

Oh, I forgot one:

* Btrfs mumble mumble handwave mumble mumble mumble snapshots mumble rollbacks. Difficulties: (1) Btrfs still isn't ready to be the default filesystem in Ubuntu (for example, it still doesn't have a released fsck); (2) no-one has time to do the work; (3) Btrfs imposes a chilling effect on people who otherwise might work on any of the other solutions.