Memory Utilization For SQK VMs Is Inaccurate From Prism Central

  • 20 October 2021
  • 2 replies

Badge +1

HyperVisor - ESXi 6.7U3

Mostly Windows VMs

I’m sure there’s good reason for this and it's probably to do with the way SQL handles memory but when I check the memory usage from Prism or Prism Central for a VM that’s running SQL it’s not accurately reflecting what the VM is actually using.  For example, from within the VM if I fire up task manager or even perfmon it will report the memory usage at say 95% whereas from Prism it reports the VM as using 25%.

I need to generate a report for a collection of SQL VMs and application servers but I think for the SQL VMs I'm going to have to provide perfmon screenshots or something.

Can anyone explain to me in simple terms why this is happening?

2 replies

Hello, This actually has to do with the way SQL server manages memory: on startup it will lock all it configured memory use depending on its requirements. By default it will take all the memory available from the OS hence the 95% in the task manager.

But this is virtual memory, so of there is no actual use, the physical memory is not ever touched, and the hypervisor sees only what is physically used by the VM.

This is a classic issues with all memory managing applications, the other frequent offender being Java and application servers.

Badge +1

Hi @PYBntnx thanks for the reply.

Yes, this is my assumption also, except I’m pretty sure SQL is actually using\touching more then 25% of the physical memory.  I can see this from within SQL, so this is where I get confused.