Blog post on Drupal load balancing, which is nontrivial. [Link]
It is not always easy to scale Drupal — not because Drupal sucks, but simply because scaling the LAMP stack (including Drupal) takes no small amount of skill. You need to buy the right hardware, install load balancers, setup MySQL servers in master-slave mode, setup static file servers, setup web servers, get PHP working with an opcode cacher, tie in a distributed memory object caching system like memcached, integrate with a content delivery network, watch security advisories for every component in your system and configure and tune the hell out of everything.
{ 1 comment… read it below or add one }
Here is a link to a scalable Drupal install in the cloud that is capable of serving a billion pages or more.
http://nscaled.com/solutions.php