Over-allocating memory to Guest OS

[digitlman77]

Hello,

On my ESX 3.5 host, I have a VM running 2003 Std x86.

The person who initially created this VM gave it 8 Gig of memory, as well as 4 vCPUs.

Since it's only a 32-bit OS, I assume that allocating more than 4G of memory is stupid? The consumed host memory is about 3.8G, so it's acting just like a real 32 OS would.

When we move this vm to ESXi 4.1, I plan to reconfiguing it properly.

[AWo]

O.K., fine. What is your question?

BTW, I would reduce the number of vCPU's to one. More vCPU's doesn't mean more processing power. Too much vCPU's can have the opposite effect.

AWo

VCP 3 & 4

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[digitlman77]

As I said, I did not set up the VM, and we'll only have 1vCPU when we migrate it.

The question is:

Since it's only a 32-bit OS, I assume that allocating more than 4G of memory to the VM is useless?

[f10]

This MSDN article indicates that more than 4GB of memory can be used provided PAE switch is enabled in the O.S

http://msdn.microsoft.com/en-us/library/aa366796%28VS.85%29.aspx

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

[AWo]

W2K3 Standard 32 bit supports up to 4 GB

W2K3 Enterprise 32 bit supports up to 32 GB.

http://technet.microsoft.com/de-de/library/cc758523%28WS.10%29.aspx

AWo

VCP 3 & 4

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[digitlman77]

Since it is 2003 Standard, it looks like PAE is not an option, and therefore adding more than 4Gig to the VM is a waste?

[AWo]

Yes.

AWo

VCP 3 & 4

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[a_p_]

Some thoughts about this:

1. As AWo mentioned Windows Standard only supports 4 GB RAM

2. Setting /PAE in the boot.ini on Windows Standard gives you access to some memory between 3 and 4 GB (I usually set this on XenApp servers). Without /PAE you may see ~3.4GB, with /PAE ~3.8GB. However when /PAE is set, each file handle will need additional memory in the paged pool. So, if you are running a fileserver with lots of open files, you better not set /PAE or you may receive errors like Server is unable to allocate memory from the system paged pool

3. If you reduce the vCPU's to just 1 vCPU you may want to replace the HAL (from Multiprocessor to Uniprocessor). If rather not want do this I'd recommend to configure the VM to use 2 vCPUs. http://www.calazan.com/how-to-change-from-acpi-multiprocessor-hal-back-to-acpi-uniprocessor-hal-in-w...

André