Note: This blog post is from 2011. Some content may be outdated--though not necessarily. Same with links and subsequent comments from myself or others. Corrections are welcome, in the comments. And I may revise the content as necessary.Did you know there's a "request execution limit" on IIS? It's 3, 10, or unlimited, depending on the version of Windows (Vista, 7, 2008) and edition (such as Starter/Home/Basic/Pro/Server).
I'll detail the limits per version/edition below.
I'll also offer a (possibly surprising) workaround that can allow you to get even more requests through IIS, even for a single web site.
(Before I elaborate on that, note that there is a separate issue if you're finding that CF doesn't let you see more than 25 requests at once. That's instead due to a setting in CF/JRun, the maxworkerthreads setting. For more on that, see this blog entry.)
That said, this is a problem which could affect anyone regardless of the app server they may be running behind IIS. (And yes, I do realize that for some, the answer to this problem will be, "see, that's another reason to run Apache." We get that. Let's just focus on this problem for those who choose/have to remain on IIS.)