If you have ever used WebTuna then you will know that we try to colour-code the performance data using a fairly standard red-amber-green (RAG) model. Red indicates poor performance and green indicates good performance. So what determines good and bad performance? Our starting point is the host or domain SLA. By default this is set at 5 seconds. For good performance the average load time for pages on that host should be less than this figure. From the SLA we derive the Apdex score, used in the dashboards and activity screens.
Now you are probably aware that in this day and age 5 seconds is actually quite generous; numerous industry studies indicate that users are expecting sub-2 second response times. But, and it is a big but, have you looked at the actual response times of your sites? For many of our customers the average is above 5 seconds. What does this mean? It means that you are going to see a lot of red. In the Apdex colour map of the world (to be released soon) the map looks like it would have done at the peak of the British Empire (or Soviet Empire if you prefer): a quarter of the globe is red.
More seriously, you are lining yourselves up for a regular stream of e-mail alerts. Alerting will also be released soon and the first mechanism is based on the SLA (there will be other mechanisms that follow later). There is a good chance that an alert will be raised on day one when the 5-second threshold is breached and it will only be cleared as the performance occasionally dips below it. As a consequence, the duration of SLA violations may be very long: they could be measured in days or weeks. This is exactly what we have seen during our Beta testing.
I would encourage our users to take a look at their performance profile and set their SLA accordingly. 2 seconds might be the ultimate aim but a more realistic SLA might be 10 seconds, especially if there is a large variation or standard deviation. This should then be brought down as you tune your site.
And that, of course, is one of the reasons you use WebTuna!