I found this article about the Google Hardware at CNet.
Surprisingly, Google is doing something so simple but so extremly smart. They put the UPS directly in the server, by placing a 12 volt battery there.
What surprised me the most is the fact that the servers do have harddiscs. I always thougt they keep all the data only in the ram to reach the speed of each query.
Read the article at Cnet incl. pictures.