VMware clarification

Can someone explain (in english) what the columns mean in the attached picture. Specifically related to RAM/memory.
Assume host has 128GB RAM.  Thanks.
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tbs_mnpAsked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Host Memory - Memory allocated to the Guest Virtual Machine.

Guest Memory % - amount of memory expresses as a percentage used by the Guest OS and it's applications.

Mem Size - Memory Size as defined by virtual machine settings.
tbs_mnpAuthor Commented:
Andrew- Could you now go one step further and disect these meanings?  How are they related / not related? Say we give the VM 8GB of RAM and the guest OS sees this as 8GB,..what does that mean for the other two metrics?  I am sure I am not making sense but what we are trying to understand is are we giving VM's too much RAM...can we scale the VM down without affecting the guest, etc...Basic VM questions 101.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Okay, so you allocate a VM - 8GB, just like in the physical world, you have a physical server, which has two DIMM slots of 4GB each.

There is a metric, you can investigate called Active Memory, this is the Guest Memory %, if you see in the example above, that over a collection period of several weeks, that your VM does not user more than 50%, or does not consume, have more in use than 4096MB (4GB), in the physical world, you could remove that 4GB DIMM, with no side effects on the physical server.

So, same is true for your VM, monitor, check, and you could if you wish remove memory.

But, if the host has 128GB RAM, you only need to start pinching memory, if you start to find you have allocated all your memory!

but there is another helpful feature of VMware..... if it finds that after you have allocated all your memory in the host, e.g. 128GB....(e.g. look at the host % free).

if you deploy another VM, of 4GB, the VMware Hypervisor, will look at all your VMs, and automatically steal memory from them to use and allocate.....

see my EE Article here

HOW TO:  Performance Monitor vSphere 4.x or 5.0

You may also want to read this document on memory management

https://www.vmware.com/files/pdf/perf-vsphere-memory_management.pdf

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