Hammer or ZFS based backup, encryption

[Csaba Henk]

Hi,

I need to setup a backup machine, and I intend to utilize today's
snapshotty filesystems (which boils down to Dfly+Hammer or FBSD+ZFS --
btrfs is not there yet, and I don't feel like dwelving into Solaris).
Set up such an OS with such an fs, and backup by syncing to the
snapshotty fs and create a snapshot.

I wonder about the following things:

1) Any idea how does this approach scale related to more conventional solutions,
like rdiff-backup or dump(8)? I see the the pros, but are there any
cons? How effective is taking regular snapshots space-wise?

2) Is there any practical argument for choosing between Dfly+Hammer and
FBSD+ZFS? (Feel free to give biased answers :) )

3) I'd like to encrypt stuff, either at device or fs level. For
FreeBSD there is geli(8). I haven't found anything for DragonFly.
Is there any way to get at it on DragonFly?

Thanks,
Csaba