Backing up external hard drive..

[darius]

How does everyone back up their external? I ended up buying a similar one with the same memory and just copied the original to the other in plans that if one goes I can use the other and then repeat the process. I would like another way to back up all 170+ GB, but DVD's are too lacking in memory, is there another inexpensive alternative I don't know about that can serve as a third copy?