Memory usage mismatch between Task Manager and VC

[Molly]

I have a VM with 4Gb of RAM running SQL 2008. Task Manager is showing 3.57Gb of Physical memory in use but VC is only showing 1.1Gb in use. Can anyone explain this mismatch please?

I'm running ESX 3.5 Update 4.

[pramodupadhyay5]

It is possible that there could be a memory utilization display

"mismatch" between vCenter and Task Manager on a given VM if large

pages are enabled on an ESX host(s). Just this week, vCenter (working

with vSphere hosts) was displaying that the memory utilization of a

particular VM was consistently between 95-100%. Looking at the VM

itself, it showed less than 37% memory utilization.

I tried

removing and reinstall VMware Tools and this seemed to correct the

problem for a little while, however, the display mismatch returned.

Though performance of the VM was normal, VMware support was contacted

to get an official answer on why this situation may occur and if they

were aware of this happening on other vSphere servers.

That's when support suggested disabling the large pages on the ESX host. Below are the steps.

1. Power off the VM which is reporting a high memory usage

2. Turn off large page on the ESX host

a) Select the ESX host from the VI Client

b) Select the configuration tab

c) Under Software select Advanced Settings

d) Select Mem and scroll down till you see "Mem.AllocGuestLargePage"

e) Set the value to 0. By default it is set to 1.

3. Restart the VM and monitor the memory usage

After performing these steps, the memory mismatch problem has not reoccured.

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[NTurnbull]

Hi, there are loads of articles around discussing the way ESX handles memory usage that word it much better than I can have a look at:

The resource management guide at

or the VMware doc for the understanding ESX memory resource management guide

To be honest it just depends how deeply you want to know how it all works

Thanks,

Neil

[Molly]

Thanks for the quick responses. I've read quite a bit on how memory is handled etc. Most articles refer to task manager performance running ok and VC reporting high performance but my issue is the other way round. The VM seems to be genuinely lacking resources as the app is not working as it should so I'm doubting what's being reported in VC. I'm not sure if giving it more resources will solve the issue though.

[NTurnbull]

VC will show you the amount of active memory actually being used by that vm on the ESX host. Maybe pages 14 and 15 of would help to find out if there are any performance issues with the vm?

Thanks,

Neil

[pramodupadhyay5]

for more help u can read this discussion

http://communities.vmware.com/message/1339407

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[firestartah]

Normally this can be fixed by uninstalling and re-installing vmtools.If that doesn’t work try:

1. Power off the VM which is reporting a high memory usage

2. Turn off large page on the ESX host

Select the ESX host from the VI Client

Select the configuration tab

Under Software select Advanced Settings

Select Mem and scroll down till you see "Mem.AllocGuestLargePage"

Set the value to 0. By default it is set to 1.

3. Restart the VM and monitor the memory usage

If you found this or other information useful, please consider awarding points for "Correct" or "Helpful".

Gregg Robertson, VCP3,4 , MCSE, MCSA, MCTS, MCITP