My network storage computer is an old Mac mini. Everything on it is replaceable via downloads, but I still prefer having a physical backup. Because it's an old machine, Time Machine on it doesn't support rotation of external drives (as Mountain Lion does). So I'm using SuperDuper instead. To get SuperDuper to support drive rotation, you need to follow these instructions: NSCoriolisBlog » Blog Archive » Rotate backup disks with SuperDuper. The one change is that it seems both the name and UUID must be the same.
(Drive rotation is so that I can always have one drive off-site. I keep one drive off-site, and occasionally swap the two drives over. Hopefully, even if everything in the house goes, I'll still have access to my data.)