How Ravelry Scales to 10 Million Requests Using Rails

7 Servers (Gentoo Linux). Virtualization (Xen) creates 13 virtual servers.
* Front end uses Nginx and HAproxy. The request flow: nginx -> haproxy -> (load balanced) -> apache + mod_passenger. Nginx is first so it can provide functions like serving static files and redirects before passing a request to HAproxy for load balancing. Apache is probably used because it is more configurable than Nginx.
(Link: How Ravelry Scales to 10 Million Requests Using Rails)