Understanding vSphere Active Memory


Do you have SQL Server instances virtualized on VMware and have a hard time understanding what the active memory settings mean? This article will help you better understand these values and what it means for you ant the servers you manage.

VMware virtual memory management was designed from the beginning with several architectural tenets in mind.  Two of those being, to leverage a share based allocation and the ability to reclaim idle memory (incidentally a great technical read here).  So when memory was in short supply, a share based mechanism could be used to determine how much a virtual machine should get in relation to its peers.  To really make intelligent allocation decisions though, an important input into that algorithm would need to be some measure of how much the virtual machine was actually using.  Existing proportional share based algorithms were quite static and ratio based.  Wanting more, Active memory was born out of the idea that if you could measure what a virtual machine was actually using, that could in turn be input into the share based algorithm making it truly proportional and therefore more realistic.  Active memory’s primary purpose is to assist in making memory scheduler allocation decisions.

You should read the entire article by Mark Achtemichuk.

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