Article: Google uncloaks once-secret server

Google's big surprise: each server has its own 12-volt battery to supply power if there's a problem with the main source of electricity. The company also revealed for the first time that since 2005, its data centers have been composed of standard shipping containers--each with 1,160 servers and a power consumption that can reach 250 kilowatts.

http://news.cnet.com/8301-1001_3-10209580-92.html