Large web site scalability: The Slashdot infrastructure hardware and software
Slashdot is a popular news site for nerds, covering technology, open source, politics and more.
While they do not run Drupal, nor PHP for that matter, they still run on a version of LAMP (Linux Apache MySQL and Perl as in mod_perl).
What is interesting is the segregation of functions on separate servers, the use of pound as a reverse proxy, using multi-master replication for MySQL, with one writeable database, limited yet efficient use of memcached, throttling and much more.
A fascinating read.
Is your Drupal site slow?