Scaling Drupal for a heavy load site

We've recently been asked by a client to look into creating a Drupal installation that can cope with heavy load. Here's some useful instructions from johnandcailin.com. I'll post a follow-up in the near future explaining what we ended up doing and how successful it was.

• Scaling drupal - an open-source infrastructure for high-traffic drupal sites
• Scaling drupal step one - a dedicated data server
• Scaling drupal step one B - nfs vs rsync
• Scaling drupal step two - sticky load balancing with apache mod_proxy
• Scaling drupal step three - using heartbeat to implement a redundant load balancer