The probable answer lies in one of Google's underground parking garages in Mountain View. There, in a secret area off-limits even to regular GoogleFolk, is a shipping container. But it isn't just any shipping container. This shipping container is a prototype data center. Google hired a pair of very bright industrial designers to figure out how to cram the greatest number of CPUs, the most storage, memory and power support into a 20- or 40-foot box. We're talking about 5000 Opteron processors and 3.5 petabytes of disk storage that can be dropped-off overnight by a tractor-trailer rig. The idea is to plant one of these puppies anywhere Google owns access to fiber, basically turning the entire Internet into a giant processing and storage grid.
While Google could put these containers anywhere, it makes the most sense to place them at Internet peering points, of which there are about 300 worldwide.
Two years ago Google had one data center. Today they are reported to have 64. Two years from now, they will have 300-plus. The advantage to having so many data centers goes beyond simple redundancy and fault tolerance. They get Google closer to users, reducing latency. They offer inter-datacenter communication and load-balancing using that no-longer-dark fiber Google owns. But most especially, they offer super-high bandwidth connections at all peering ISPs at little or no incremental cost to Google."