OpenFlow is going to change data centers as it redefines the network. Look at the company Nicira that was started by the professors who defined OpenFlow.

One of the demonstrations of OpenFlow is ElasticTree which can be used for lower energy use in the data center.

The ElasticTree paper is here.

The authors had access to data from Google.

It looks like this team had access to Google data centers back in 2008.

Traffic in a Realistic Data Center
In order to evaluate energy savings with a real
data center workload, we collected system and network
traces from a production data center hosting an
e-commerce application (Trace 1, §1). The servers
in the data center are organized in a tiered model as
application servers, file servers and database servers.
The System Activity Reporter (sar) toolkit available
on Linux obtains CPU, memory and network statistics,
including the number of bytes transmitted and
received from 292 servers. Our traces contain statistics
averaged over a 10-minute interval and span 5
days in April 2008.