Drupal performance and scalability

I've been doing some research and testing with Drupal measuring performance and scalability. Drupal has built in CSS and JavaScript aggregation (now in D6) to minimize the number of http requests, and caching via the database. In some cases with a high amount of traffic caching with the database is not enough. Modules like Cache Router allow the site caching to be handled by an engine other than the database to increase performance for larger amounts of traffic. Some popular engines that are used with the cacherouter module are APC or Memcache. Each have their advantages and disadvantages although for large scale sites with multiple web heads memcache seems to be the better choice with the ability for all of the web heads to share a single cache and not having to worry about synchronization as with APC. Both are fairly easy to set up and get going on *NIX systems and most Linux distros have both available in the package repositories. I recently ran into this presentation on line and I think it does a good job summarizing how to setup a scalable, high performance Drupal site.

• Scaling Drupal: Not IF... HOW