From CNET:
CHICAGO--On the outside, Microsoft's massive new data center resembles the other buildings in the industrial area.
Even the inside of the building doesn't look like that much. The ground floor looks like a large indoor parking lot filled with a few parked trailers.
It's what's inside those trailers, though, that is the key to Microsoft's cloud-computing efforts. Each of the shipping containers in the Chicago data center houses anywhere from 1,800 to 2,500 servers, each of which can be serving up e-mail, managing instant messages, or running applications for Microsoft's soon-to-be-launched cloud-based operating system--Windows Azure.