To support over 500k users, you *need* - A 64 bits hardware/kernel (AMD64, Opterons) - At least 8GB of ram - A recent linux kernel (2.6.x) About tuning, I prefer to not fully disclose them because servers are targets of many attacks, so it's better not help hackers. The most touchy thing is the IP route cache : You have to tune it or else the machine drops many connections (hint : rhash_entries=... in the boot append string) hints : echo 1 > /proc/sys/net/ipv4/route/gc_interval echo 150 >/proc/sys/net/ipv4/route/gc_timeout echo 2 >/proc/sys/net/ipv4/route/gc_elasticity - Use of hugeTLB pages hint : echo xxx >/proc/sys/vm/nr_hugepages Tune tcp : echo "4096 49152 131072" >/proc/sys/net/ipv4/tcp_wmem echo xxxx >/proc/sys/net/ipv4/tcp_max_syn_backlog echo xxxx >/proc/sys/net/core/somaxconn echo 1200000 > /proc/sys/net/ipv4/tcp_max_tw_buckets echo 7 >/proc/sys/net/ipv4/tcp_retries2 echo "600000 650000 700000" >/proc/sys/net/ipv4/tcp_mem echo 0 >/proc/sys/net/ipv4/tcp_timestamps echo 0 >/proc/sys/net/ipv4/tcp_window_scaling echo 0 >/proc/sys/net/ipv4/tcp_sack echo 330000 >/proc/sys/net/ipv4/tcp_max_orphans echo "10000 62000" >/proc/sys/net/ipv4/ip_local_port_range others : echo 1300000 >/proc/sys/fs/file-max