IIS6, ASP.NET MVC 1 and random slowdowns

I've recently deployed a MVC application to an IIS6 web server. One strange behaviour I've been having is the load times will randomly blow up to 30sec+ and then return to normal. Our tests have shown this occurring on multiple connections at the same time. Once the wait has passed, the site become responsive again. It's completely random when this will occur, but will probably happen about once every 15 minutes or so.

My first thought was the application was being restarted by the web server for some reason, but I determined this wasn't the case because the process recycling is set very infrequently, and I placed some logging in the application startup.

It's also nothing to do with the database connection. This slowdown happens simply by moving between static pages too. I've watched the database with a SQL profiler, and nothing is hitting it when these slowdowns occur.

Finally, I开发者_运维问答've placed entry and exit logging on my controller actions, the slowdown always happens outside of the controller. The entry and exit time for a controller action is always appropriately fast.

Does anyone have any ideas of what could be causing this? I've tried running it locally on IIS7 and I haven't had the issue. I can only think it's something to do with our hosting provider.

Is this running on a deadicated server? if not it might be your hosting providor.

It sounds to me from what you have said that the server every 15 mins is maxing its CPU for some reason. It could be something in code hitting a infinate loop, have you had a look in the event log for any crashes / error from the application.

Run the web app under a profiler (eg JetBrains) and dump out the results after one of these 30 seconds lockups occur. The profiler output should make locating the bottleneck fairly obvious as it will pinpoint the exact API call which is consuming the time/blocking other threads.

At a guess it could be memory pressure causing items being dumped from cache or garbage collection, although 30 seconds sounds a little excessive for this.