easy, centralized backups?

[David Feldman]

I have a small home office network composed of several OSes. My primary 
machine is a Mac, and I do backups via Retrospect to DVD. I recently 
converted my girlfriend's Dell to a dual-boot Ubuntu/Win configuration, 
and am trying to do as much from Ubuntu as possible. In the past I've 
backed it up by running the Retrospect client on it and backing up from 
the Mac. Retrospect does have a Linux client but only for Red Hat. So, 
I'm looking for suggestions regarding the best way to back up from 
Ubuntu that integrates into my existing system. I can think of a few 
options, but don't know if there's something better:

(1) Use a separate Linux backup tool to back up to an archive or set of 
archives on the Mac or a shared machine. Then back up the archive via 
Retrospect. Relatively easy, but may eliminate the possibility of 
incremental backups since I'm not sure Retrospect does differential 
backups of individual files.

(2) Mount volumes from the Ubuntu machine on the Mac via SMB or NFS, 
then back them up as though they were local volumes.

(3) Reboot into Windows and keep doing what I've been doing (yuck).

Any ideas?

Thanks,
--Dave