Memory Resource Allocation - Host vs Guest Memory

[rprime]

Hi all

I have read multiple topics about this, but nothing specific to what I have to ask.

I understand that Host Memory is the amount of RAM that a VM is using from it's host and Guest Memory is supposed to represent the % of that host RAM the guest is using.

My question comes in here... I have a SharePoint VM that has 8gb RAM allocated and the Guest Mem % is ~20%.  But if I check Task Manager/PerfMon on the VM console, the guest is sitting at 7.5g.  I am looking to upgrade it's resources which is why I started poking around in here but I am confused as to how this Guest Mem % can possibly be accurate.

Is this a common issue where this counter is inaccurate or am I missing something?

Thanks for your time and assistance!

Ryan

[chriswahl · Accepted solution]

The host uses an "active" memory algorithm to determine how much memory the VM is actively using.

The VM guest OS shows committed memory to running applications and processes.

These two will rarely be the same.

[rprime]

Thanks Chris.

Can I interpret this to mean that they're both accurate but in different ways?

Ryan

[stinklyonion]

it means that they are both important, rarely the same but have different role when checking VM memory.

[chriswahl]

rprime - Correct. Typically something like SQL server will consume the majority of guest memory (from the guest OS perspective) but not necessarily be actively used (from the Host perspective).