Get a Drobo if you want a completely hassle-free unit. It's well worth the money if you want something easy that just plain works. They are easily upgradable (with zero downtime, in fact) and require zero setup or maintenance. I've had three since they first came out - a beta/pre-production unit, 1st gen, and 2nd gen.
I'm not affiliated in any way with Data Robotics, but they have a really great product. I can answer questions if you're considering one, just ask.
http://www.datarobotics.com/