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I know the answer to this is "it depends", and I know that the counter can and will be thrown off by backup jobs or other things that might use memory mapped files. I'd like to get a bit of clarity over exactly what "it depends" on and some general guidelines around what a healthy web server normally shows for this counter.

So if activities regarding memory-mapped files are excluded, if I have ample amounts of memory, should I really see this down close to 0? When should I get suspicious that I might need additional RAM and/or start looking for application memory leaks?

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3 Answers 3

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You should monitor your application with something like smokeping. This will tell you when the application becomes slow and alert you. You can also use Cacti (or other monitoring software) to record requests per second, the number of threads... etc. You should monitor also the database (locks/second, select/insert/update per second etc...). Monitor the network traffic and disc queue length. Become familiar with the load of your application and thy to find the bottlenecks and reproduce them in a lab environment if possible. Load test with JMeter.

For an application the best pages/sec under load test was 30 pages/sec and we were very happy. For another application 60 pages/sec was the load under normal traffic. And under the load test the maximum was about 250 and we were working to improve it.

See:

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the "It depends" should be expanded to "It depends on your application". The best thing you can do is to load test your application (if you can't setup an exact mirror take some downtime) to find the breakpoints for your particular setup.

There are many tools out there to do this.

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This is helpful I suppose, but a mention of a couple of tools, or pointer to a list of tools, would be more helpful. –  LarsH Aug 6 '13 at 12:46

On our heavy loaded, dual-quadcore ASP/ASP.NET webserver we experience a few spikes, but the average for the last two years is exactly 8.5098, so yes it's quite close to zero. Spikes (one or two every three months, I dunno what they are) are around 2k.

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