Under the Covers: Architecture at AnandTech and the Performance of ASP.NET

Scalability of the website

Since the site went live with the new ASP.NET framework, we've constantly been monitoring the servers and tracking statistics, and to say that we've been impressed is an understatement. We've had near 99% up-time and have seen dramatic increases in performance and scalability of the site infrastructure. Each of our clustered servers use an average of 12% CPU, and each server has at least 450 users on them at any given time. Pages execute in an average of 15ms, which is 60-80ms better than what we used to do.

To track our statistics, we wrote a performance counter monitor that resides on each server. It essentially writes the output of various performance counters to an aspx page, which we then feed into a database and run reports, view trends and monitor new versions of the site code as they are put into play.

Last week, we performed a test on scalability, to see how scalable one server was in the cluster. We monitored a server in the cluster for a period of 10 minutes while all five servers were in the web cluster. Next, we shut off four of the servers leaving one to serve the load for the website. Below is a table of the before and after of this test - impressive results in our opinion.

Performance Counter	Before (5 servers in the cluster)	After (1 server in the cluster)
CPU Usage	5%	30%
Concurrent Users	450	2400
Requests per second	12	80
Average request time (ms)	15	18

As you can see, ASP.NET is very efficient. CPU usage climbed to 30%, not much considering nearly 2000 more users were on the server. Request per second were 7 times higher and our average page request times were still approximately the same, showing the efficiency of the ASP.NET runtime and the scalability of the website itself.

The migration has been successful, but there is always something else to do with a site of this size. We have a meeting at CES in January to talk about future plans. There will be, more than likely, new functionality to plan for and architect (what I live for). We're also going to take a look at a possible firewall upgrade next year. We've managed to hit our 18,000 simultaneous sessions limit twice in the past few months; once, we sustained 65Mbit/second of throughput for a few hours.