SuperDuper!
From Amahi Wiki
A little info on SuperDuper! It is free, but some features are locked in the free version, like scheduled backups and other sorts of things.
Personally I do use this (bk) and I did pay for it, it is a great backup solution for over a network, however, it is very slow. Backups to a network volume are saved as Read/Write bootable sparce images.
They have a wonderful feature though, its called Smart Update. Smart Update allows for the next time you backup, it only backs up the changed files from the last backup, which makes it alooot faster.
<h>If you feel that this is slow and want to change, try backing up with your Mac device plugged up with an ethernet cord for the first time, after that backups over the wireless AirPort will be a breeze. (I have talked to the maker and he said that backups that big over wireless are common to be very slow, he recommended I backup as well with an ethernet cord the first time.)More info and steps on backing up to your Amahi HDA will be coming soon, as I get into the device more and more and really get down to how it works.