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MrVmware9423
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Consumed Host Memory vs Active Guest Memory

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nava_thulasi39
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Hi,

Again, this is also explained in the same Duncan Epping Blog : http://www.yellow-bricks.com/2010/12/20/vcenter-and-memory-metrics/

From the blog

Consumed Host Memory is the amount of physical memory that has been allocated to the virtual machine. This also includes things like memory overhead, that also means that Consumed can be larger than what has been provisioned. To make it a bit more complex it should be noted that in the “Performance Tab” the “Consumed” Counter doesn’t actually include Memory Overhead!

Active Memory more or less already explains it, it is what the VMkernel believes is currently being actively used by the VM. Now it should be pointed out here that this is an estimate calculated by a form of statistical sampling.

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nava_thulasi39
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Hi,

Again, this is also explained in the same Duncan Epping Blog : http://www.yellow-bricks.com/2010/12/20/vcenter-and-memory-metrics/

From the blog

Consumed Host Memory is the amount of physical memory that has been allocated to the virtual machine. This also includes things like memory overhead, that also means that Consumed can be larger than what has been provisioned. To make it a bit more complex it should be noted that in the “Performance Tab” the “Consumed” Counter doesn’t actually include Memory Overhead!

Active Memory more or less already explains it, it is what the VMkernel believes is currently being actively used by the VM. Now it should be pointed out here that this is an estimate calculated by a form of statistical sampling.

If you find this or any other answer useful please consider awarding points by marking the answer correct or helpful
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shishir08
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People usually confuse between Physical memory and Machine memory. The stats and accounting are different between the two layers.

Physical Memory Stats:

-Active, Balloon, Granted, Shared, Swapped, Usage

And Machine memory Stats:

-Consumed, Overhead, Shared Common.

Guest physical memory can be greater than machine memory due to memory overcomitment and page sharing. Memory Consumed is the actual amount of Machine Memory that has physical memory mapped to it. Active memory is the allocated memory which has been accessed recently or used by applications and idle memory is the one which has not been accessed recently.

There is also a concern among customer should we be looking at "active" memory, or "consumed" memory for a VM?.

For measuring over-all efficiency, look at memory consumed (or granted).

For analyzing memory usage of individual VMs during a short period, look at memory active. This value is actually calculated through statistical sampling. This means that the ESX selects a random subset of the guest’s memory and monitors how many pages are accessed in a certain interval. This value is than extrapolated to the full size of the guest’s memory and shown as guest memory usage. Why is there a difference between this guest memory usage value from ESX and from inside the guest? This is because the guest’s OS has a much better visibility of what memory is actively used. The ESX hypervisor can only use sampling to guess the “active” memory size.