title: Perfmon ASP.Net Apps "Sessions Active" Counter
body: <p>EDIT: We realise that the sessions we're reviewing at the moment are inproc, and that's absolutely fine. The question, in a nutshell, is are the sessions active as reported in the inproc counter reliable as they are delivered? Or can they look higher than they actually are for any reason (I read a piece about it appearing to be in the region of 400 million or something due to the installation of ASP.Net 3.5 but I'm not talking that high).</p>
  
  <p>At my place of work we're trying to ascertain how many people have an active session on a moment to moment basis as the number of active sessions is the trigger for a piece of load balancing software that activates an appliance. We're looking at the Asp.Net Apps "Sessions Active" Counter and it seems to be giving some slightly odd readings when we compare how many people appear to be browsing our site versus how much business we're actually doing. It is possible, for example, to register only 1600 active sessions but be selling items roughly every two minutes or, like this morning, to top 3000 active sessions but only be making sales every 15 minutes.</p>
  
  <p>It is entirely possible that we just have a lot of lurkers but to be sure I wondered if anyone knew how this counter actually arrived at its figures and whether it is susceptible to any kind of false positive behaviour. I've been keeping an eye on the perfmon figures for a couple of hours now and the sessions active has veered between 3100 and 2700 but in all that time we've made about ten actual sales. Should we be taking it as gospel that we just have a lot of browsers?</p>