Many Web pages are comprised of content from a variety of sources. The base page (i.e. the HTML of the main page) may draw in content from one or more Content Delivery Network (CDN) providers, multiple ad providers, widget providers, partners, etc. When a page shows degraded performance, how do you quickly identify who is responsible?
Stoyan Stefanov came up with the idea of a Performance Advent Calendar, and is posting an article each day on Web performance. I have the honor of contributing this guest post, repeated below.
-Eric
When trying to quantify the performance of a Web site, we most commonly mean the response time. The two most common methods of gathering response time data are from Field Metrics and Synthetic Measurement.
To quantify the performance of Web sites, there are lots of metrics:
And metrics provide a great deal of insight. But sometimes we get lost in the metrics. Sometimes metrics alone don’t tell the whole story. What we need is a picture.
If you’ve spent any time making Web sites faster, you’ve undoubtedly come across the work of Steve Souders. In addition to working at Google, speaking about Web performance across the world, and teaching a class at Stanford, he finds time to write books!
Steve’s first book, High Performance Web Sites, was one of the first of its kind to assemble and codify the best-practices for improving Web site front-end performance. His latest book, Even Faster Web Sites, picks up where the first left off, and dives even deeper into performance optimization techniques.
Again this year, the Velocity Conference was a huge success. Exceeding last year’s attendance, more than 700 people came together in San Jose to geek out on Web Operations and Performance.
A focus this year was the impact of Web site performance on business metrics, such as revenue - putting some teeth into why performance matters.
We know the various rules for improving Web site performance. But are sites employing them? Which rules are used most? What impact are they having?
The webpagetest.org site (powered by AOL PageTest) has been active for nearly a year now, and has collected performance metrics for more then 20,000 Web pages.
Pat Meenan recently reviewed those results, looking at the cummulative distributions of various metrics and optimization scores. The results are pretty eye-opening.
Ran across a blog post from Jesse Robbins, and this quote really struck me:
Web Performance & Operations is an emerging discipline which requires incredible breadth, focusing less on specific technologies and more on how the entire system works together. While people often specialize on particular components, great engineers always think of that component in relation to the whole. The best engineers are able to fly to the 50,000 foot view and see the entire system in motion and then zoom in to microscopic levels and examine the tiny movements of an individual part.
Spot on.
More goodness in the rest of his post.
Last year’s Velocity Conference was fantastic! More than 600 folks attended, from all corners of the Web Performance and Operations community. It was the epicenter of knowledge for making things faster and more reliable on the Web.
This year’s conference program looks even better. I’ll be attending and presenting again this year. If you’re a performance or operations geek, and looking for like-minded individuals, you need to be there.
Pssst. Use this top-secret code during registration to receive a 15% discount: vel09cmb. But you didn’t get it from me. 
I was talking with some really smart folks recently about performance metrics. We started with “what” and “why” - what metrics do you collect and why (i.e. what do you do with them). After some discussion, one of the participants said:
I first learned of Apdex at CMG 2006 and led a pilot project within my company to understand how we might use it. I presented my experience at CMG 2007. At that conference, I ran into an acquaintance, Neil Gunther, who had begun working with Apdex and alternate visualization techniques.
Neil has now published one of the most comprehensive discussions I’ve seen on Apdex: The Apdex Index Revealed.
