Performance Tuning Backend Apache

1. Faster processors won’t improve performance all that much; most Web servers spend up to 90% of their time waiting on disk I/O. As soon as you start swapping, performance will just die. Faster disks might help slightly, but they’re much more expensive than RAM, such that it doesn’t really matter.
2. Serve static images using a stripped down light weight apache server, lighttpd, or squid cache.
3. Consider using a CDN (such as akamai) if possible. CDN often use Geo-distributed DNS that reduce distance / latency (static contents load faster)
4. Turn off Keep-Alive. Keep-Alive is a feature of HTTP that allows multiple HTTP requests to be served over a single TCP connection, avoiding the TCP setup/teardown overhead. This looks good at first glance, but it can kill the performance of a Django site. If you’re properly serving media from a separate server, each user browsing your site will only request a page from your Django server every ten seconds or so. This leaves HTTP servers waiting around for the next keep-alive request (a request that might or might not come within the keep-alive timeout), rather than serving pending requests (request that already arrived from another browser).

http://www.devside.net/articles/apache-performance-tuning
http://people.redhat.com/alikins/system_tuning.html