graeme_p - 4:55 am on Sep 6, 2010 (gmt 0)

You can use rsync and a perl script to keep rotating snapshots with minimal duplication.

You can use rsync for the initial copy as well.

I would also suggest using a USB external drive. That way you will not have both drives corrupted by a bad controller, or simultaneously trashed by a power surge or motherboard fault.

This is what I do, and I also do a network backup. I use the grsync GUI front end for rsync for both.