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We have a vsphere cluster and we are trying to setup monitoring via Foglight to monitor memory usage at the Guest level.

However, there are inconsistencies in reporting metrics.. most likely due to lack of knowledge.

These systems run SAP and are all running Red Hat Linux

For instance:

running top on a single server returns 10GB used memory. When looking in Foglight it shows active memory is only ~2-3gb.

Can someone explain why top would read more usage than Foglight, and vice versa?

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Perhaps learn something about vmware's memory works and the difference between a hypervisor's view of memory and the more limited view from within a guest. BTW this site is for professional sysadmins, who generally know the basics and can do their own research before posting here, maybe read the FAQ. – Chopper3 Jan 17 '13 at 18:00
Trying to get a SAP stack exchange started, check it out… – TheRandomSuit Mar 14 '13 at 18:57

Active memory in VMware is equalent of memory that has been recently paged. It shows you how much load your VM is putting on the physical host in terms of memory utilization.

Please read the following articles:

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