Crux of my question: When I look up web gardens on the web, I can find all sorts of articles that tell you what they are, how to set them up, etc. I can't seem to find anything that says, "This is the performance counter/metric that you need to monitor to tell whether or not you need a web garden." Can anyone help me understand how to know when it's time to move to a web garden model?
Why I ask the question: We have a site that serves ~20mb downloads from a single IIS 7.5 server (win2008R2) - users come to the site, register for an account, and download our software. We are using ASP.NET 4.0 and use ASP.NET's TransmitFile to send the file. Our server is a fast server w/ 8 CPUs and a 1gbps NIC hosted through <big monitored server company> (so we feel infrastructure is not a problem). Our server is set to the default to use one process (not a web garden). We do use session InProc also. App pool is set to .NET 4.0 Classic.
One problem that I *think* I notice is that, when a user with a slow connection downloads a file, this will impact other users' ability to download. Our single server is located in the US and, when someone from Australia downloads, the time might be 15 minutes. During this 15 minutes, there seems to be an issue when other users connect and try to download. A few users seems to be able to do so just fine but there does seem to be some point (at which exact point, I'm not sure) when the long-running download causes the site to not respond quickly. I monitor the NIC utilization and it's fine - 3% max.
I wish my IIS knowledge and diagnostic ability was better - I can't say that I can spot these problems, nor can I force-reproduce them in such a way that I can see an error. I also don't get errors in the log. I just know that it happens - we have a log analysis app that (a) finds "long-running requests" and then (b) shows us the other requests around that time period. It's obvious that the long-running request is causing the other requests to take longer. Inevitably the long-running requests are a user from a slow connection or halfway-across-the-world downloading our software. I've optimized as much as I can in ASP.NET and now it's a matter of trying to see if there's something in IIS that I can learn to help me troubleshoot better. I'm wondering if the long-running download is creating a blocked process in IIS that, if I expanded the number of processes, would remove this problem.
Thanks!