Host memory usage , when host is not in over committment state

[john23]

Hi,

My ESX host has 256 GB physical ram, I have 17 vm running in it.

Total allocated memory to vms :176 GB.

When I generate a performance chart for host memory usage (1 month), the percentage is coming almost same as allocated memory to vms

My understanding is, if server has enough physical ram available, then Host memory usage is almost (2-3% vary), comes equivalent to vm memory allocation only.

I checked the same trends on 5servers (which are not overcommitted).

From VMTN folks, I want to know: is this the correct calculation??

Thanks

-A

[weinstein5]

Can you provide screen shots of what metrics you are looking at - the server with 256 GB does not seem to be overcommitted

[john23]

weinstein,

I will try to get from my client.

Servers are not over-committed.

-A

[john23]

Please find the screenshot, Host has 255 GB memory and no overcommittment

[GMCON]

I can't quite tell what you are looking for here is what i think you are asking for.  Host is not overcommited, Host memory usage is practically equal to guest allocation plus a little bit more because of overhead.  This would be a correct assumption.  From the screenshot above as an example if you are using Windows OS as guests then what happens is Windows touches all it's memory on boot up which is why you will see guest memory consuming all of the memory allocated to it.  Since your host is not overcommitted and has plenty of memory to spare it will not try and reclaim any of those resources from those guests.  Hence why your Host consumed memory is always showing very close to what your allocated memory is.  Does this make sense?  Let me know if this answers your question.

[john23]

Can you provide any reference doc for this?

[GMCON]

Here is the overall guide for how VMware implements memory techniques.  You can look on page 14 for a small snippet how when to reclaim resources are done but honestly to get a good overall understanding you will have to read more of the documentation

http://www.vmware.com/files/pdf/mem_mgmt_perf_vsphere5.pdf

Here is also a good post by Frank Denneman which is old but the percentages are still good and give a good overview.

Memory reclamation, when and how? - frankdenneman.nl

Let me know if this helps and mark as helpful or solved if it does.