Windows or *nix?
Most Linux distros ship with tools that would make this a sinch (tar, mkisofs and dvdrecord). However if you want backups like that, a DVD won't get you that far. I would suggest investing in a tape drive, its money well spent (but buy the RETAIL version unless you're absolutley sure that the software you already have will do the trick - I bought an OEM drive and it was just the bare drive, no software or drivers. Windows wouldn't touch it, but it gave me an excuse to move my fileservers to Linux

)