BACK UPS?? CD? DVD? HD? Do you trust it?

I use Retrospect to back up my DP sessions. It works really well and is very configurable and adaptable to multiple backup formats.

All I use with it at the moment is an offline firewire hard drive. DVDs are too small, slow, and cumbersome. I want to get into a digital tape backup system, something with very large capacity eventually, to run at the very end of a large project. I have suffered drive failures and stupid human error, etc., and Retrospect has always been there to rescue my sessions!
 
Apple+S or Ctrl+S nonstop during the session, and back up at the end of the night. I prefer not to interrupt the artist's flow with computer shit. If you're on a long one, you could always perform a backup during a break.