Disaster Receovery Plan

I would personally recommend to you a product we use called Snapback Live by Columbia Data Products. It is the only product I know of to take a true image backup of the drive. The beauty of this method is that if your system goes down, you simply restore the tape and you have a fully working system again. You do not have to reinstall or reconfigure anything. It also allows you to mount the tape for file-by-file recovery if necessary. It is fast, easy to use, and I believe cheaper than other solutions.
This product is ideal if you have a standalone server, or a tape drive in each server. It is not capable of backing up over a network. Also, your tape must be large enough to hold a full image of the drive (compression is used of course) as each backup is a full backup. In a typical PDC/BDC setup it may not be necessary to back up the BDC. If you wanted, you could ghost the BDC to a shared folder on the network or something.