We can support up to 2000-3000 or so users with one PHP box (Dual Xeon 2.6Ghz 2GB RAM) and one MySQL server (Dual Xeon 2.8Ghz, 4GB RAM, SCSI RAID)... but it gets spotty in that range. The PHP server starts getting very slow.
At MWSF we cloned the PHP server across many instances of Amazon's Elastic Compute Cloud, and then we found that the MySQL server dies at 5000-ish users.
This time, we added a server for Memcached, PHP (+ EC2 clones), and single MySQL server and hit the 6000 users.
There were some errors though due to some PHP instances not working out right for some reason. we'll try to sort it out for next time.
We can support up to 3000-4000 or so users with one PHP box (Dual Xeon 2.6Ghz 2GB RAM) and one MySQL server (Dual Xeon 2.8Ghz, 4GB RAM, SCSI RAID)... but it gets spotty in that range. The PHP server starts getting very slow.
I guess we can just be glad the you guys are staying on top of understanding how to keep the servers running under all this traffic. I never really considered the volume of users posting here. I knew about traffic issues on Keynote days but even keeping up the boards is probably pretty intense!
I am assuming because they are so expensive. It is cheaper to build a cheap box with those specs then to buy an Xserve. Plus you can download Linux and throw it on there to perform the same task as an Xserve would do.