UPS == Uninterruptable Power Supply --> what Korrd said.
Actually most UPS solutions are only designed to keep the box running for a few minutes, to get through brownouts or to allow for graceful shutdown. They're not designed to keep the shop running for hours until the power comes back on. Not when you have dozens of servers sucking down 500kVA.... that's what a generator is for:D
Course in Majk's case it's moot, as he's not likely to be beside the Disco server 24/7 to shut it down if power goes out.