We are running WordPress on our multi-platform cluster and this is what we use for performance settings in nginx.conf

worker_processes 20;

events {
worker_connections 20000;
use epoll;
}

worker_rlimit_nofile 25000;

Nginx is a front-end and for backend we use Apache, however we will soon try different set-up using different architectures.

The client servers are 5400 Series Intel XEONs with 8GB RAM running Linux and SATA hard drives.