We are running Drupal 6 on a LAMP stack on Ubuntu on a single box. The Drupal configuration is pretty much an out-of-the-box config, but we have a number of modules we have added. We started bumping up against memory limits on our box with 2gb ram (we have since upped the memory as a short term fix). Today, for instance, we had 206 simultaneous users using our app at peak.
We will be building out a load-balanced site with a separate db server, but I would still like to get a feel for how much headroom might be available to us on each web server box if we put enough time in tweaking the configurations. I realize there is no 'typical' configuration, so I appreciate that another's experience does not directly apply to my site. However, I would like to get an overall feel for the range of what others handle with Drupal on a single box; how much memory does your box have and how many requests per unit time do you handle? In our usage patterns, we see very sharp spikes in usage over short periods of time (like 10 minutes), so data about peak requests per second handled would be great. What is a reasonable range for the number of simultaneous requests a Drupal server with 2gb of memory might handle. Am I way out of line thinking I could handle 200 simultaneous requests per second with a 2gb server? Thank you for you input.