You should have a tape drive for backup. Ideally, your tape backup should be able to image your entire disk. Choosing a tape drive used to be pretty complicated, with a plethora of different formats and media to chose from.
Some people like to burn CDs for backup.
While this is a good way to archive precious data, the capacity is too low and the media cost too high for serious use. Rewritable CD-RWs do make a very nice transfer medium, however. I'm told that Hewlett-Packard DDS devices are especially good, not surprising given HP's traditional obsession with reliability and overengineering stuff. All the DDSs I know about are SCSI devices. Don't forget to put the cost of cleaning tapes into your budget.