One of the most successful projects I worked on used static HTML generation. It was a company-wide system status site, so it needed to be up no mater what, no matter what type of issues we were experiencing. Using this approach we didn't have to worry about database issues or anything. Just static HTML hosted by a CDN offsite.
Hmm yeah, my stuff doesn't use a database either (it uses XPath and DOM/XML doc). Is it standard for CDNs to run anything beyond a naked apache instance (like mod_php)?
It seems like a giant can of worms to introduce mod_php. Do you allow sessions? Replication? How do you handle caching? These are non-trivial problems at CDN-level loads.
Offering 100% availability is crazy difficult once you add dynamic content into the mix. If you could do it, I bet you could make a million bucks.
Availabity with dynamic content is easy (ok not easy, but it's a fairly routine straightforward process). The CAP theorem says you get 2 out of the 3 of consistency, availability, partition tolerance. Just getting availability and partition tolerance by themselves is just a matter of good engineering, nothing revolutionary.
