Here're my running notes from Nelson Minar's Google is Harder Than it Looks talk at the O'Reilly Emerging Technology Conference in San Diego.
Query comes into custom httpd, Google Web Server ("gwis")
Sent in parallel to several places:
* Index server, "every page with the word 'apple' in it — a cluster that manages "shards" or "partitions" (everything starting with the letter "a") and then load-balancing replications for each. Have to calculate intersections for multiple-term queries
* Doc server, copies of webpages — whence page-snippets are served in results. Sharded and replicated for scaleability and redundancy
* Misc servers: QuickLinks, spell-checkers, Ad server (first two are small servers, ad server is humongous)
