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I've seem some claims that Exchange (link) and Elasticsearch (link) can suffer from "too much" memory. I also read a vague hint in an old book that the same might be true of IIS:

[T]he more [RAM] the merrier, at least to a certain degree. If you have too much RAM, the IIS file cache cannot use it fully. Therefore it might be good not to exceed 2GB to 3GB of RAM for a standard Web server.

Can anyone confirm or refute the claim that an IIS server can have too much RAM? If the claim is true, is it a matter of fine-tuning the configuration?

The reason I ask is because I am seeing a possible performance issue in my production vs test environments in which the test environment, even under heavy load, seems to perform better with 16GB of RAM than the production which has 64GB. I am running IIS 8 on Windows Server 2012 R2 64-bit.

(The only ServerFault question that I could find doesn't address IIS specifically.)

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anon
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    That book is 12 years old. I'm reasonably certain IIS saw improvements since then. The 2-3 GB recommendation sounds very much like it's a 32bit issue, which would certainly no longer be an issue. – ceejayoz Oct 27 '16 at 14:32
  • @ceejayoz - Good point! I thought that 2-3GB seemed quite low, but I didn't notice the age of the book. I'll edit the question to point that out. – anon Oct 27 '16 at 14:38

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There are a lot of things to consider.

How much traffic are you expecting concurrently?

How complex is you site/apps?

IIS doesn't have much overhead the app/site will have the overhead.

There really is not rule of thumb when it comes to how many sites/connections vs how much ram.

On the database server however it is great to have as much ram as the size of your databases to allow the databases to run out of memory.

I have seen severs running 2500 very small website 2 / 3 pages with 3GB of ram and IIS using about 750mb of the ram.

I have also seen server clusters running 1 site and needing 64GB of ram or more to keep up with the worker process.

The only time I have actually seen a server do worst with more ram was running ColdFusion 9 because of garbage collection bug, they fixed the garbage collection in 10.

When considering RAM don't forget about the RAM for the OS and do some load testing.

Mike Meidl
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