ASP.NET and memory consumption

We have a production environment wher开发者_开发技巧e we host more then 100 sites, consisting of .net 3.5 Web Applications.

We are unable to keep every web site in memory because the total required memory size is larger then the available RAM size + paging size.

How i can minimize used memory by web application ?

Settings :

• Windows 2008 r2
• IIS 7.5
• ARR 2.5

Some ideas:

if you can modify the applications,

• try to make them as stateless as possible (i.e. don't use session state, if not absolutely required)
• reduce useage of cache, output caching and application state

if you cannot modify the applications,

• reduce the session timeout so that sessions expire quicker
• move to out-of-process session state (state-server or sql-server) on a different machine
• configure IIS to unload applications when they are inactive
• buy more memory :-)