Update 5: PlentyOfFish Update - 6 Billion Pageviews And 32 Billion Images A Month Update 4: Jeff Atwood costs out Markus' scale up approach against a scale out approach and finds scale up wanting. The discussion in the comments is as interesting as the article. My guess is Markus doesn't want to rewrite his software to work across a scale out cluster so even if it's more expensive scale up works b