Redundant backup drive recommendations?

I’m having a real problem with multiple copies of pictures being spread across multiple computers. I want to be able to put all the pictures on one virtual drive that represents multiple hard drives, so that I can keep all the pictures in one place with no copies.

I’m pretty sure that Drobo is the easiest backup drive to use, but I want to get one that’s just cheap and reliable. Does anybody have a recommendation? I don’t really mind whether it’s just the case or it has drives already in it. I can plug in a hard drive…