Microsoft has released a 12 page document that describes, at a high level, how Microsoft manages their own internal infrastructure.
This is just the latest in a series of these "How Microsoft do …" documents to be released. I can’t recommend enough that you read them if you are carrying out similar projects. You’ve possibly heard how Microsoft "eats their own dog food". MS IT will deploy MS products long before they reach the public. By doing this they can test the products but they also learn the best ways to deploy and use them and share this information via whitepapers, TechNet, best practices documents, seminars and MS Press. Reading these documents gives you a different perspective … telling you why the driving factors or decisions were for their designs. Plus you get a handle on how the product scales.