问题
In IIS 7, what is best practice? Should I create an application pool for each application, or should I share an application pool with as much application as possible?
Are there any performance drawbacks or security issues related to one of the options?
回答1:
Each application pool is an instance of W3wp.exe, a worker process for that site or set of sites. By placing each application in a seperate app pool, you ensure that problems that could potentially cause problems within the app pool do not cause problems with other applications. There is obviously an overhead to operating like this in terms of resources.
So generally, for simple sites and blogs I usually put these in a shared app pool. For more intensive or important applications, I seperate into individual app pools. This is just a guide to how I operate.
I believe IIS7 now creates seperate app pools when you create a web site (not 100% though).
回答2:
In theory it is better to put each site to its own pool. In practice it takes much more RAM than placing the sites to a single pool. So, on most servers you will see 10-100 pools only, even if there are 1000 sites.
回答3:
Sharing Application pool is better than creating an application pool for each application for a fixed number of application
You can run as many application pools on your IIS 7 server as you need but this will affect server performance.On the other hand Application pools allow a set of Web applications to share one or more similarly configured worker processes but you should not share an application pool to a lot of application.Because This will affect your server performance too!
So in both way you have to be tactful.
来源：https://stackoverflow.com/questions/7553088/what-is-best-practice-in-iis-one-application-pool-for-each-application-or-a-sh