Wednesday, May 27, 2009

RAM - performance bottleneck? Check 'PagesOutput/Sec'

http://support.microsoft.com/kb/555223

Memory, Pages Output/Sec - this shows how many virtual memory pages were written to the pagefile to free RAM page frames for other purposes each second.
This is the best counter to monitor if you suspect that paging is your performance bottleneck. Even if Committed Bytes is greater than the installed RAM, if Pages Output/sec is low or zero most of the time, there is not a significant performance problem from not enough RAM.

Memory, Available MBytes - this measures how much RAM is available to satisfy demands for virtual memory (either new allocations, or for restoring a page from the pagefile).
When RAM is in short supply (e.g. Committed Bytes is greater than installed RAM), the operating system will attempt to keep a certain fraction of installed RAM available for immediate use by copying virtual memory pages that are not in active use to the pagefile. For this reason, this counter will not go to zero and is not necessarily a good indication of whether your system is short of RAM

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