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 from October 1, 2005 - November 1, 2005, in reverse date order:
Probability: The Rain in Spain ...
Today I was going to write about probability theory, statistical independence, and correlation, and their importance when analyzing performance data. But I know those subjects have a tendency to induce severe attacks of fear and loathing. So instead I'm going to talk about the weather -- specifically about the difference between British and Californian weather.
Chris Loosley
in Foundations of Performance
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The Value of Reference Models
Without a shared language, communication is impossible. A reference model establishes a shared foundation -- a frame of reference, or conceptual framework -- that can then be used to structure subsequent discussions of a subject. For more details online, the best resource I found is a discussion of the OASIS SOA Reference Model. Its focus is different from ours, but it contains some good general points, including:
Chris Loosley
in Performance Management, Standards (Apdex, ITIL, etc.), Foundations of Performance
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Sharpening the Saw
If you've read The Seven Habits Of Highly Effective People by Steven R. Covey, then you may remember that the seventh habit is Sharpening the Saw. The idea is that you should always allocate some time for personal renewal.
Chris Loosley
in Life, The Universe, and Everything
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The Web Site Response Time Model
Response Time Model
Yesterday I introduced a reference model for Web site availability, and promised to write more about its uses today. But I have since decided to first introduce the equivalent model for Web site response-time. Then I will compare and contrast the uses of the two models, because -- although similar -- their application is not identical.
Chris Loosley
in Performance Management, Foundations of Performance
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The Web Site Availability Model
Availability Model
I am a mathematician at heart, and all mathematical conclusions are derived by deductive reasoning from a set of an initial set of assumptions (postulates or axioms). So it is natural for me to want to establish a clear foundation on which to build any discussion of performance matters.
Chris Loosley
in Performance Management, Foundations of Performance, Availability Management
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The ABC's of Measurement Data
In my experience, companies usually have lots of measurement tools. Granted, some of them do sit on the shelf unused, but many are in use -- some even collecting data continuously. Despite all this data gathering, the value obtained from the data is often a lot less than it might be. Data is meaningless unless it's interpreted and applied; as a medieval scribe might have said, graecum est; non potest legi. Today I will describe a framework for addressing this concern.
Chris Loosley
in Performance Management, Measuring Performance, Reporting on Performance
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Performance: Déjà Vu All Over Again
A few days ago, an email from TeamQuest offered me their new white paper on The Renaissance of Performance & Capacity Management in the 21st Century. The email points out that anyone involved in IT for a reasonable amount of time understands that the IT industry is cyclical and says that a data center renaissance is coming full circle.
This got my attention, and not only because it is redundant (coming full circle implies rebirth, the meaning of renaissance). But we've learned to live with worse, especially in direct mail. Anyway, what makes this particular life-cycle so interesting to me is that I have actually participated in it at every stage.
Here is my Cliff Notes version of TeamQuest's history of Capacity Planning:
Chris Loosley
in Articles and White Papers, Performance Management
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Delight, Satisfy, or Frustrate?
Web page download time and site usability
Two recent posts (here and here) have discussed the relationships among user expectations, site responsiveness, and user satisfaction. As a general rule, people's perception of a site's quality and credibility diminishes as its download times increase.
So what are the implications of this research for an organization embarking on a program of Service Level Management (SLM) or Web Performance Management? How do you keep users satisfied?
Chris Loosley
in Business Perspectives, Performance Objectives
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WYSIWYG, or No Site is an Island
Customer expectations of Web page download times
When writing about Human-Computer Interaction (HCI), I discussed Robert B. Miller's classic research into computer responsiveness and its relevance today to questions of Web site design and site usability. For one response to Miller's findings (by providing more percent-done indicators and busy cursors) see Jakob Nielsen's Web site and his best-selling book, Designing Web Usability.
But Miller's three thresholds are far from the whole story ...
Chris Loosley
in Foundations of Performance, Performance Objectives
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The Miller Response-Time Test
Web page download time and usability
In the field of Human-Computer Interaction, HCI for short, one crucial and much-studied aspect is the speed of the computer's response to various kinds of user inputs. Although a few of these studies do get quoted in discussions of Web site design and Web usability, most books and articles on these topics devote very little space to this aspect.
One of the best summaries appears in Andrew B. King's book Speed up Your Site, which opens with the simple observation that People hate to wait. His first chapter (Response Time: Eight Seconds, Plus or Minus Two) includes a brief history of HCI research into the influence of computer response time on user satisfaction (or frustration), and an overview of its relevance to Web site usability.
Chris Loosley
in Foundations of Performance, Performance Objectives
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