Nine students are in one class, a single one in another. What’s the average class size?
Five, obviously: (9 + 1) / (1 + 1) = 5.
It’s a trick question, though. Consider the viewpoint of the students: nine of them say, “my class has nine students”, and one says, “I’m all alone”. The calculation of average that corresponds to these facts is (9 * 9 + 1 * 1) / (9 + 1) = 8.2.
So is the average class size 5, or 8.2? The difference is considerable–64%–and when it appears in calculations of cost-of-living indexes, or compliance agreements, or drug trials, or any of a number of other quite serious areas, it’s a difference that can easily make a difference. The precise details of even such apparently-simple definitions as “average” or “delay” can swing numbers more than the signal we’re trying to detect!
While the made-up numbers of this “classroom size paradox” are easy enough to understand, they simultaneously illustrate an aspect of Application Performance Management (APM) that’s often hard to communicate. Many organizations cultivate an attitude that cost–how big a budget is, how many people or machines are involved in a plan, or how many months it takes to achieve a result–determines the importance of a matter. This becomes so ingrained that it’s hard to imagine a different approach to management.
APM is one. APM focuses on the result or benefit of an application, in terms of its end-user experience (EUE). That’s a different way of thinking, as different as considering a classroom from where the students sit, rather than looking out from the front where the teacher stands. Even a subtle shift in perspective, though, has the potential to yield conclusions that otherwise are invisible. As important as traditional measurements of filesystem performance, network congestion, and database speed are, EUE cannot be reduced to these components. APM has a unique role to play in both of its emphases on EUE “looking in”, and its holism for measuring end-to-end factors.
APM has fallen out of fashion among pundits over the last year, in large part simply from the overstimulation of so many other hot topics, like bigdata and cloud, to absorb. “Application Monitor” will return through December with more explanations of the irreplaceable value APM provides. Most important is the way it stands up for end users as no other metric does. You need that perspective.