[Erwin]

My servers are running FreeBSD 6.0 AMD64 without any problems on Quad Opterons and Dual Processor/ Dual Core Opterons. Initially we had the wrong kernel compiled so only 1 CPU was recognised, but this was picked up quickly - we now run the 64bit SMP kernel, and the forums have never been faster.

FreeBSD is an awesome OS - the ports system is easy - install portmanager and you can easily install ports using single commands - say goodbye to problems with rpm dependencies. It's also fairly easy to customise, and is secure.

I documented everything I did to set up a FreeBSD server, so if anyone wants help, let me know.

Also, I'm running Lighttpd instead of Apache - this is a fantastic webserver, much leaner than Apache, and is fast! It also load balances php by running php as separate processes - you've got to try it out to believe the difference in speed and reduction in server loads.