Sharing .NET application pools [duplicate]

Question

On an server running multiple ASP.NET sites, is it better to use one application pool per site or for sites to share a single application pool? What are the advantages or disadvantages inherent to each setup? Or is there a hard and fast rule here?

Answer 1

This really depends on what the requirements are of the site, as well as your concern regarding risks.

When two applications run inside the same application pool they have the same security level, so there is a security concern here for some as in theory each could have access to files of the other. Also, if one site starts having issues and using memory it could cause recycles or freezes that could impact both.

Although there is not a "hard and fast" rule to this, some of the things that I consider and that cause "automatic" decisions for me are the following.

• Is the application mission critical? (If so, separate app pool)
• Is this a third party application? (If so, and unsure of what all it does, separate app pool)
• Will this application see major spikes in activity? (If so, it might be best to isolate)

There is a lot out there, but the keys are isolation and ability to troubleshoot single applications. Here is a Microsoft article that touches on it a bit as well.

Answer 2

One of the advantages of separate AppPools is that in the event that you need to recycle the AppPool you can do so for one site without affecting the performance (or caching) of the others.