[UM-LINUX] Home backup system

[Derek Juba]

I'd like to get some suggestions on a backup system for my home PC.  
Currently I have two identical drives set up in RAID 1 mirroring, but 
I'm looking to change this since it doesn't protect against my 
accidentally deleting or screwing up a file.

I was thinking of just setting up a cron job to mirror one drive onto 
the other every night, but I'd like to avoid copying all the unchanged 
files every time, and it would be nice if I could store multiple 
revisions, as space permits.

Does anyone know of some good software to do this?  It almost seems like 
it could be done with something like subversion, though I don't think 
you can delete old revisions from an svn repository very easily.

-Derek