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Vsphere guest VM uses massive memory for doing nothing

Posted on 2010-11-09
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Last Modified: 2012-05-10
Hi,

I Have a virtual machine that runs smooith. It is a windows 2003 32bit R2 server. It runs on Virtual Center 4.1

It has 1 CPU and 512 MB RAM

When I add one CPU and give it 4GB RAM, It uses up to 3 GB RAM. When before it used 256MB RAM

How can I fix this?
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Question by:sayadi
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by:jdfulton
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I assume you have rebooted the server after making the changes?  Also is the VMware Tools up to date?  What process on the server is using all of the memory?  You can see this using Task Manager.
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by:sayadi
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Yes I did rebooted or else the CPU would not be seen by the windows.
Show all processes from all users is checked and all the processes combined it does not even add up to 400 MB.
VM tools is also up to date.

Now - an hour later - the total amount of memory in use is 1200MB
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bgoering earned 500 total points
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In the boot.ini on your server you need to add

/PAE

to the end of the boot line for it to recognize all 4 GB. I believe it needs to be Enterprise Edition to use this, otherwise 3GB is it.

See http://support.microsoft.com/kb/283037

Good Luck

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by:jdfulton
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Windows Server 2003 supports up to 4GB of ram without any customization so I don't think the previous comment is correct.  So it sounds like it is an issue between Windows and VMware.  VMware is not reporting the correct memory usuage correct or is Windows saying it is using the memory?  If you can provide screenshots of where you are seeing this it may be helpful.  I would try uninstalling VMware tools and reinstalling next.
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by:bgoering
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@jdfulton - PAE is only enabled automatically in 2003 if the memory is hot-added. Otherwise you have to explicitely add the switch. I had the impression the machine was taken down, reconfigured, and brought back up - if so not hot add event was ever raised.

@sayadi - You need to look at the performance tab in the vSphere client to see what the actual memory consumption is on the vm. Windows may "think" it is using a lot, but VMware is pretty good at reclaiming physical memory that isn't being actively used while letting the guest vm believe that it still has it. Several techniques are used by VMware  You can refer to http://www.vmware.com/files/pdf/techpaper/vsp_41_perf_memory_mgmt.pdf for the details of how memory is utilized and reclaimed.

Good Luck
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by:coolsport00
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Are you wanting to see how to get RAM usage down, or are you wanting your VM's OS to see all 4GB of RAM? In other words, are you seeing performance issues based off RAM usage and want to decrease RAM usage? I think some posters are suggesting how to get your VM OS to 'see' all 4GB RAM, but from your orig post, it seems your wondering why your VM is using 3GB RAM whereas before it used barely any (256MB)? Please clarify...

Thanks.

~coolsport00
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by:sayadi
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coolsport00 you are right. The issue is why it's using so much memory.

The fix for high memory support in windows solved the recondition problem. But it's still using way to much memory.
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by:sayadi
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Hier is an screenshot
screenshot.doc
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by:sayadi
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@bgoering
in the performance tab the same amout of memory is claimed.
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by:coolsport00
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According to your screenshot, you have a MS Service (obviously unsure specifically of which one) and "MCShield" using up a lot of memory. A quick Google of"MCShield" states that it's a process used by McAfee. So, I can only assume that is your memory issue...that app/process and the service that goes with it. Disable it then moniro your memory usage to see if it goes back down.

~coolsport00
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by:sayadi
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That is the Virus Scanner. Now using 114MB, but it does not add up to be 2500MB+ total consumption.
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by:coolsport00
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Ok...misread the usage; click on the Performance tab and check memory usage there....see how much is actually being used.

~coolsport00
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by:bgoering
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At boot up time Windows will look at the total RAM available after OS and all services have been started. Then it will claim a large percentage for file buffering - this memory is initialized to binary zeros. This shows up in the task manager with the Physical Memory Cached value. As time goes on if it is not being used Windows may reduce the cached pool if it is not being utilized. For example, if the Windows machine is not doing much in the way of being a file server Windows will reduce that value. Take a look at http://technet.microsoft.com/en-us/library/cc778082(WS.10).aspx for the description of the performance counters for the core memory object in Windows 2003. Using perfmon you can dig a bit deeper into how the memory is actually being utilized.

However, VMware recognizes this Windows behavior and will not actually allocate all of that to real physical RAM unless it is really needed. If you refer to the document I referenced in an earlier post to this thread you can get a full description of the various techniques VMware will use to manage the physical RAM on your system.

Hope this helps
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by:sayadi
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Large memory support in windows was the problem

http://support.microsoft.com/kb/283037/en-us
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by:sayadi
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issue solved
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