Enthusiast
Enthusiast

Memory counters meaning in vCenter and capacity planning

Hi all,

Can you please confirm the below

1/ Can you confirm that “Virtual Machine Memory Usage” shown in the vCenter GUI is all the same here :

guest mem - % = memory usage ( summary page of VM ) = Memory (%) usage ( performance tab of VM ) = Host consumed % ( at VM level in performance tab / advanced ) =  active ÷ VM memory granted ?

I refer to following

https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=10026...

Capture.PNG

I’m less sure about host consumed %

2/ How is calculated the memory used as show in summary tab of a host

Capture.PNG

Is following correct

  • Memory used = memory consumed ÷ total machine memory amount
  • And consumed memory = total host memory - free host memory

  • So Is it correct that Memory used depends only on the sum of allocated memory given to each powered on VM by the admin + all overhead.

3/ For capacity planning, should you size the memory of VMs based on the average memory usage at VM level or based on memory usage at guest level..

Guest memory usage is always much higher ( example task manager in windows ), and virtual machine usage ridiculously small in vsphere.

I understand that looking at memory usage in the guest is more reliable for capacity planning.. ( even for HA reservations sizing )

Though VMware appears to say that memory sizing should be based on the memory usage at vsphere level :

A virtual machine's memory size must be slightly larger than the average guest memory usage.

https://docs.vmware.com/en/VMware-vSphere/6.0/com.vmware.vsphere.monitoring.doc/GUID-5E6E062F-7ECE-4...

4/ So should one size to a memory size slightly larger than the average memory usage as reported by guests ?

5/ Then if it is not for capacity planning or HA reservations planning, why it useful to show this kind of VM memory usage in the first place  in the GUI ? how useful for an administrator is it if they don’t reflect what VMs really use,

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VMware Employee
VMware Employee

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