The other thing about redundant systems is that you have to pay attention to failures.

Agreed. I take a walk at least every two days by the servers I help manage at work. No red lights, I keep walking, otherwise I check to see what the failure was. Redundant fans, power supplies, and hard drives all make it very clear when they fail.

One day I'll get the agents loaded on the machines so they can just page me. That way, noone using these servers will ever notice any failures.