It is an interesting summary that links together a bunch of information buried in a lot of sources. As David said near the start of the article:
Google has a split personality when it comes to questions about its back-end systems. To the media, its answer is, "Sorry, we don't talk about our infrastructure."I am briefly quoted on the second page of the article, unfortunately nothing particularly insightful.
Yet, Google engineers crack the door open wider when addressing computer science audiences, such as rooms full of graduate students whom it is interested in recruiting.
As a result, sources for this story included technical presentations available from the University of Washington Web site, as well as other technical conference presentations, and papers published by Google's research arm, Google Labs.
Make sure to clickthrough on the "Next" link on each page so you see the entire article. It's 14 pages long. If you want it all on one page, the printer-friendly version is here.