Server Power & Performance:
A Buyers Guide To Upgrading Your System

Date: January 14, 2004
Author: Jason Rabel

Real Life Scenario:

One of our web / database servers was hitting an unusually high load level and suffering from poor performance during peak hours of website traffic. After tuning the OS and application as much as could be, the server would still run out of physical memory and thus be forced to swap to virtual memory. As soon as it started swapping to virtual memory was when the load levels started to increase and performance decrease.

Simple solution? Add more RAM to the system. (You knew I was going to say that.)

We contacted Crucial Technology about our situation, and a few days later we had a 1GB PC2100 ECC Registered DIMM ready to install in the server.

The web server used is Apache, which generates dynamic web pages based on data from the MySQL database. The database holds anywhere from 5-10 million rows of data at any given time! Caching data plays a key role in keeping performance at acceptable levels for the users. The requests are generally for the same lumps of data, potentially requesting thousands of rows of data initially, which must be aggregated together and summarized down to something that is human-readable.

Even though this is a production server, it was taken out of the loop long enough to run some performance comparisons before and after adding in the extra gigabyte of memory. Instead of using synthetic benchmark programs, which don't really reflect what this server does day-to-day, I chose to use a program called siege. Here's a quick quote from the author's site about siege:

Siege is a http regression testing and benchmarking utility. It was designed to let web developers measure the performance of their code under duress, to see how it will stand up to load on the internet. Siege supports basic authentication, cookies, HTTP and HTTPS protocols. It allows the user hit a web server with a configurable number of concurrent simulated users. Those users place the web server "under siege."

Siege is very configurable, settings like concurrent users and repetitions allow you to simulate an entire day's traffic in just a matter of seconds (hence the name "siege"), so one must be careful using this tool as it can be very easy to overload a server. Also instead of requesting just a single page from the server, a file can be created with a list of URLs to request during the test, thus making it more accurate of a simulation of real (and random) traffic.