Collected thoughts about software and site performance ...

Web performance matters. Responsive sites can make the online experience effective, even enjoyable. A slow site can be unusable. This site is about online performance, how to achieve and maintain it, its impact on user experience, and ultimately on site effectiveness.

Home | Entries about Blogs and Publications (27), in reverse date order:

Generalizing The Apdex Standard [2]

Illustration: Apdex Logo

Today the Apdex specification is entirely focused on application response time. Its first paragraph defines Apdex as “a method for calculating and reporting a metric of transactional application response time in the form of an index with a value of 0 to 1.” But in reality, the Apdex method has much wider applicability. A more appropriate description might be the general statement that Apdex is a metric that reflects the degree to which a set of performance measurements achieves designated targets.

The idea of generalizing the Apdex standard has been discussed periodically within the Apdex community. To turn those discussions from an abstract idea into a concrete proposal, I’m writing a series of posts on the Apdex Exchange blog ...

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Apdex as a (Key) Performance Indicator

Illustration: Apdex Logo

On the Apdex Exchange blog, I’m writing a series of posts about Generalizing The Apdex Standard. The ideas I developed (together with any public input) will evolve into a new draft of the Apdex specification. The latest post is on Apdex as a (Key) Performance Indicator. Here's a brief introduction:

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Measuring Mobile Web Sites

Illustration: Web Analytics Report

The methods commonly used to measure Web sites often don't work for mobile sites, because of differences among mobile platforms and devices. The biggest obstacles are lack of support on mobile devices for Cookies, JavaScript, and client IP addresses.

The Wikipedia article on Mobile Web Analytics provides a succinct introduction to these and other challenges -- see the section on "Problems with tracking visitors, visits and clickpaths in the Mobile Web". Because of these limitations, the tagging methods used by traditional Web analytics tools do not work on most mobile devices.

While researching this subject, I discovered Kaizen Analytics, an excellent blog by Michael Notté. In a recent post, Michael provides a useful overview -- see Mobile Analytics: vertical-specific vs. traditional Web Analytics solutions. Michael points out that there are other ways to collect data about mobile Web sites. He outlines four solution approaches, illustrating each with a helpful diagram:

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Generalizing The Apdex Standard

Illustration: Apdex Logo

Today the Apdex specification is entirely focused on application response time. Its first paragraph defines Apdex as “a method for calculating and reporting a metric of transactional application response time in the form of an index with a value of 0 to 1.”

But in reality, the Apdex method is much more widely applicable, and a more appropriate description is already spelled out in the first paragraph of the Wikipedia article on Apdex ...

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Why Technorati is Not Usable

Illustration: Four dimensions of usability

I was going to write about performance and availability today, but this was not the post I had in mind. Technorati sidetracked me. So I'm going to write about Usability instead. Because Technorati provides a good counter-example -- how not to build a usable Web application that satisfies and retains customers.

In Web Usability: A Simple Framework, I described a way to think about Web site or Web application usability.

In a second post, The Dimensions of Usability, I presented the graphic shown here, and discussed the four dimensions in a bit more detail.

These four dimensions are not alternative functional goals, to be weighed against one another and prioritized. Web application effectiveness is a four-step challenge:

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Human Factors and Blog Design

The best products are designed with Human Factors in mind. That's why I often write about Web design and usability in my Web Performance Matters blog.

Jeff Atwood recently published Thirteen Blog Clichés, a post summarizing his "opinions about what makes blogs work well, and what makes blogs sometimes not work so well." These are presented as a list of common mistakes to avoid (or anti-patterns). If you have a blog, or are designing one, you've probably read similar articles before. Even so, Jeff's checklist is worth a look. All such lists tend to contain a core set of common guidelines to follow and/or pitfalls to avoid, but some of Jeff's opinions step outside the conventional wisdom.

Because I maintain two blogs -- Web Performance Matters and UpRight Matters -- I decided to rate both blogs against Jeff's criteria. Here are edited versions of his recommendations, and my responses. To read Jeff's full discussions of each guideline, see the original. And for the full story, see the many responses posted by Jeff's readers in the comments section of his blog.

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Posted on Saturday, September 22, 2007 at 12:30AM by Registered CommenterChris Loosley in , | CommentsPost a Comment

Scalability is Not Optional

Illustration: Kent Langley

My recent post, Asynchronous Architectures [4], summarized a presentation by Werner Vogels at the 2007 QCON conference in London.

A subsequent post by Kent Langley in his new ProductionScale blog -- entitled Getting Rid of the Relational Database -- supports the arguments advanced by Vogels.

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Latency, Bandwidth, and Response Times

Illustration: Web Page Response Time 101

Latency, Bandwidth, and Station Wagons focused primarily on the limitations of network bandwidth, and the time required to transmit massive data volumes. While that is an interesting topic, and one that produces some surprising results (like the fact that FedEx is still faster than the Internet), it is not particularly relevant to the subject of Web performance, which depends on the time required to transmit many small files.

My post highlighted It's Still The Latency, Stupid, by William (Bill) Dougherty in edgeblog. Bill's title pays homage to a famous 1996 article by Stuart Cheshire about bandwidth and latency in ISP links, It's the Latency Stupid.

Over a decade later, Bill points out, Cheshire's writings are still relevant: One concept that continues to elude many IT managers is the impact of latency on network design ... Latency, not bandwidth, is often the key to network speed, or lack thereof. This is especially true when it comes to the download speeds (or response times) of Web pages and Web-based applications. In this post I explain why, providing some supporting references and examples to support my argument.

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Latency, Bandwidth, and Station Wagons

Illustration: Station Wagon

One concept that continues to elude many IT managers is the impact of latency on network design. 11 years ago, Stuart Cheshire wrote a detailed analysis of the difference between bandwidth and latency in ISP links [It's the Latency Stupid]. Over a decade later, his writings are still relevant. Latency, not bandwidth, is often the key to network speed, or lack thereof.

That's from It's Still The Latency, Stupid by William (Bill) Dougherty, writing in edgeblog on May 31, 2007. Bill follows that opening paragraph with a very readable explanation of the vital importance of latency (round-trip time) as a factor affecting performance in TCP networking. He uses what he calls the Sandbag Problem to illustrate his points:

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Distributing Java Applications

Illustration: a checklist

Testing Anti-Patterns

Clustering and distributing Java applications has never been easier than it is today. As a result, writing good distributed performance tests and tuning those applications is increasingly important. Performance tuning and testing of distributed and/or clustered applications is an important skill and many who do it can use a little help.

That paragraph introduces a new series of four posts about how to approach testing for distributed Java applications by Steve Harris of Terracotta, who blogs as DSO Guy. Steve frames his guidelines as anti-patterns -- in other words, pitfalls or "commonly-reinvented bad solutions to problems" to be avoided [see Wikipedia].

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