High traffic: Serving 500,000+ unique visitors in 24 hours and over a 9,000,000 a month
Recently a client we helped get started with Drupal and admin their backend systems for, had their first 500,000+ unique-visitors day.
Everything went well, the lessons we've learned over the years of Drupal performance tuning (Part I, Part II), combined with well planned Apache/MySQL/PHP settings provided an event-free day (other than watching the hit counter go through the roof!).
Showing that it was no fluke, the site has had numerous 500,000+ days since then and has settled into an average of 150,000-200,000 unique views a day / 6,000,000-9,000,000 visitors a month.
If you have a Drupal site that you need to prepare for high traffic and high availability, give us a shout. We can help you handle it.