He does not mention it, bug ZFS has great support for snapshots (compared to e.g. LVM snapshots). You don't have to carve out disk space in advance where snapshots are stored and they are relatively high performance, so you can have an hourly, daily and weekly rotating set of snapshots (there are some scripts around for that retention). As the snapshots take up space, your available disk space just diminishes. And you can set it up so while in you are in dir "foo", your "foo/.snapshot/16:00/" has the contents of that directory when shapshotted hourly.

Another cool feature: you can do a send a diff between 2 snapshots as a file stream (over e.g. SSH) and replay it on another machine. So that's like using rsync except it's actually a stable snapshot (rsync can't fully handle files that changes while it's copying them) and you don't have to re-checksum every part of every changed file. So you can use that for DR.

Transparent compression is also great (as is deduping -- if you have tons of spare memory!)

BTRFS will be able to do the same thing... one day.