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While learning SharePoint, I noticed that, an IIS manager consist of Application Pool tab and Websites tab. Both includes the names of web application created. I could not understand the difference between these two.

It would be of great help, if someone could share a brief idea about the differences.


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up vote 8 down vote accepted

An application pool is a collection of websites running as a single process, with a single identity. You can have multiple websites running under a single application pool, but you can not have a single website running in multiple application pools. Splitting websites over application pools allows more rigid security between the sites, as well as preventing one website from crashing if another one does. The benefit of combining multiple sites into a single application pool is to either share resources, or to leave a smaller server footprint on the server.

You can find more information here:

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Thanks a lot for the info – Thomas Mathew Aug 10 '11 at 12:30
a website is at the root level comparable to a virtual directory. and per virtual directory you can create an app with its own app pool. just to clarify the statement a bit. – Marco Scheel Aug 10 '11 at 14:26
What Marco said is true - my statement was talking about SharePoint websites (Web Applications) specifically, in which virtual directories are very rarely used. The Office Web Apps / Web Services application, however, may well be a single site with many virtual directories, each with their own app pool. It depends on your implementation. – Mike Redden Aug 11 '11 at 0:41

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