In the Java world, I often see separation between web server and application server. The idea is to scale out your “relatively” cheap web server easily and beef up your application server when needed.
However, I don’t see this setup in the .NET/windows 2008 world all the much, why is that? One argument against this architecture in the .NET world would be the licensing cost of IIS7/W28. Is there any reason why .net developer/architects are not going after this design?
There was no clear concept of “Application Server” in .NET. Also .NET is very good “integrated” with OS
We can say that so far the role of application server was on IIS and Windows.
You get almost everything you need packed in .NET framework itself.
Also note that from April 2010 you can use AppFabric which is Application Server. I have started evaluation of this product and it looks to be really good.
So if you are interested in application server for .NET please have a look at AppFabric.