I can tell you from experience in the last two weeks, that you can only have ONE worker process per application pool. And how did I find this out..
Well, firstly - although I have 8gb of memory, on my dual core, dual 3.2 XEON processor, which I think should be substantial enough. But I'm having some "memory exceeded" with the amount of traffic the server is getting apparently, so, several new application pools were created where the settings were allowing up to 4 worker processors. I wasn't aware of this, since I hadn't set it up, but let me give you some examples behaviour.
- Containers were affected - I would change a container to find that intermittently it would display the previous container, and no amount of ctrl refresh, clear cache would help.
- Store functionality- Catalook would not operate correctly
- Tabs would be there and then not
- Skin changes would not be reflected, no mattter if i opened in Opera, IE6, IE7 or Firefox on different computers.
- I could log in, then I couldn't log into sites
Because I didn't set this change, my technical guy did, not knowing the repercussions, I swear I thought I was going mad. I cleared my dns cache, reset my network connection, restarted the system, restarted IIS, changed the web.config file to reset it.
The ONLY thing that stopped all this from happening was to set the worker app to 1 per pool. I can now setup 100 different pools if I want,using the same wp3exe with no problems, but I cannot and will NEVER EVER run with more than 1 per application pool.
What a horror that was. Not only did it disrupt my work, but it eats into your time substantially and we all learn from it.
And I do have to thank John Mitchell - what a tremendous wealth of knowledge he as, as well as patience I explain in perhap not the best manner, and with less courtesy than I display on the forums, just how I'm feeling about something at that particular time.
So I hope this will give you an insight to something I feel might be of assistance to others.
Nina Meiers