According to an article in Wired, Barroso had never designed a datacenter until he received this request from Google. He came up with the concept of "datacenter as a computer", building data centres with low-cost components, as we know them today.
He comments that the lack of experience in datacenter design may have been an advantage, as we questioned almost every aspect of how these facilities were designed. Perhaps the most important thing was having the opportunity to look at the entire design, from the cooling towers to the compilers, and this quickly revealed important opportunities for improvement. Barroso’s idea quickly spread throughout Silicon Valley, among the datacenters of other Internet giants.