For those interested in how we run Fabulously40.
1. Single server, OpenSolaris / 8Gigs RAM / Quad Xeon x5355 / 100Mbit line.
2. Static and dynamic data cached up front on varnish
3. Even though Nginx can handle L7 load balancing, Perlbal offers better flexibility with its plugin system
4. Jetty application servers easily scale out by using memcached as the session store
5. Write intensive operations are done asynchronously via the ActiveMQ message store system
6. One PostgreSQL database on RAID1 with a hot standby database on a third disk.
There you have it.