Monitoring RAM, under and oversubscribed VM's

[Gaprofittit]

Hi All,

I have a question regarding memory usage, I have used numerous tools and third party tools for memory management, all seem
to pull Active vs Consumed memory metrics from Vmware.  These don't jive with what the guest OS reports.  The other
day I had a developer tell me his server was tanking, I looked at the metrics in Vmware for Guest OS and reports
from the third party tool, memory consumed was 800MB, Active was 283MB.  I logged into the Windows Server 2008
and the system was pegged for 6 hours at 1.99GB of 2.0GB allocated ram.  The VM is allocated 2.0 GB with no limits etc.

How am I suppose to accurate report on this for VRAM entitlement and make sure RAM isn't under or over allocated? The
only option I can find is traditional server monitoring, Nagios, etc.

Thanks,

Greg

[logiboy123]

My guess is that transparent memory page sharing is causing you problems. This is not uncommon in an oversubscribed environment.

When I run into problems like this my first resolution step is to give the VM a memory reservation for the minimum amount of memory required for the application to run properly. Have you tried this step?

Regards,

Paul

[weinstein5]

It sounds like your are observing the affects of Transparent Page Sharing but not enought reosurces assigned to the VM -If the users are complaining of performance issues I would increase the amount of RAM assigned to the VM and if there seems to be contention for memory indicated by excessive ballooning I would then set a reservation for the VM.

To vRAM - you can do this under the licensing tab - but with the values you give it looks like this VM has a vRAM of 800 MB the memory consumed but remember the vRAM you are licensed for is a 12 month moving average - 

[shishir08]

People usually confuse between Physical memory and Machine memory.The stats and accounting are different between the two layers.

Physical Memory Stats:(Guest Level)

-Active,Balloon,Granted,Shared,Swapped,Usage,

and Machine memory Stats:(Host Level)

-Consumed,overhead,Shared Common.

->Be careful not to mismatch physical and machine stats.

->Guests physical memory can be greater than machine memory due to memory overcomitment and page sharing.

->Memory Consumed is the actual amount of Machine Memory that has physical memory mapped to it.

     Memory Consumed = Memory Granted - Shared Pages

So if the sharing of pages between the VMs is less then Memory consumed value will be  very high.

Memory size presented to the guest can categorised in two way.

1) Allocated memory-Memory assigned to applications.

        Further it can be categorised in two ways:

               a) Active Memory-Allocated memory recently accessed/used by application.

               b) Idle Memory- Allocated memory recently not accessed/used by application

2) Free memory-Memory not assigned.

HTH