I use it for two reasons. The first is generic: I work only on filesystems with data checksumming; the current ones are BTRFS and ZFS, and I have a low opinion

I use it for two reasons. The first is generic: I work only on filesystems with data checksumming; the current ones are BTRFS and ZFS, and I have a low opinion of the developers/development of the former. The second is specific: I keep my disks encrypted; since v0.8, ZFS has encryption integrated, which allows me to have disks encrypted and mirrored without additional layers (BTRFS requires LVM for this setup). In the past I've also used snapshots, by the way, which are really functional.