What server configurations can benefit from Drupal performance tuning and optimization?

There are some assumptions made before we can help with tuning your setup.

• You are on a cluster of dedicated servers, a standalone dedicated
  server, or a VPS at a minimum.
• You do not have full control of a shared host, and hence whatever tuning will be limited to Drupal itself, not Linux, MySQL or Apache.
• Your site is on the machine(s) that will be used when the site goes live. If your site is yet to be launched, the tuning will be limited if you have no traffic, or you are still on a development machine different from the machine(s) that will host this site. This limits the scope of tuning that can be done and only certain things about the site can be revealed.

In these cases, the review will not reveal all potential bottlenecks, specially ones that would reveal themselves under load.

This is not to say that such a review is completely worthless, but rather that it has limitations that you should be aware of.

A followup tuning exercise is recommended after the site has been live for sometime, on the machine(s) that will host it live.