将IIS与APACHE相比。现在都模块化了，认证是一个大头，连接数请求数是个大头。资源消耗也是一个大头。性能监测也必不可少。
配置文件也要方便处理，进程隔离也要考虑。。。。。
http://www.codeproject.com/Articles/28693/Deploying-ASP-NET-Websites-on-IIS-7-0
以上这个文篇讨论得比较基础，但有利于建立系统概念。。
The following diagram shows the Overall Architecture of IIS 7.0 which contains HTTP.Sys, SvcHost.exe, Application Pool and Worker Process(W3Wp).
The main components of IIS 7.0 are HTTP.Sys, Svchost.Exe, Application Pool , Worker Process (W3WP.exe) and Configuration Store.
HTTP.Sys: It the Kernel mode Protocol stack which listens to the HTTP and HTTPS Request. W3SVC and WAS are the parts of Svchost.exe. W3SVC is the Listener of Request from kernel mode that is passed by the HTTP.Sys. W3SVC also interacts with Windows Activation Process which is managed by the worker process by starting, stopping and recycling the application pool. It was also responsible for Health Monitor of Application Pool during runtime. Configuration stores all web.config and ASP.NET Settings and other configuration in XML Hierarchy form. W3wp.exe is a long-running process that processes requests and generates responses.
The following diagram shows you the process flow of IIS 7.0. This is the flow of User Request to IIS and gets the Response from IIS.
User Request Pass from Kernel Level to User Level Via Http.Sys and then passes to svchost, and then goes to Application Pool.
For more details, please click here.