How many CPU-cores can I use?

[andi303]

Hi all,

I've installed a VM with Windows 7 on an ESXi 4 host:

• I can select up to 8 cores in the VMs settings.

• ESXi 4 is licensed with a vSphere Advance license key.

However, the VM still only shows 2 CPUs with 1 core each. Can I only use two cores in ESXi4, even if I'm using a vSphere license?

If so, why can I select up to 8 cores?

Thanks in advance,

Andreas

[Dave_Mishchenko · Accepted solution]

The number of vCPUs can be assigned is determined by the license level - http://www.vmware.com/products/vsphere/buy/editions_comparison.html, but you still need to take into account the guest OS CPU licensing. Windows will see 2 vCPUs as physical CPUs and thus just use them. To get around that you have to use the cpuid.corePerSocket setting - http://www.yellow-bricks.com/2009/06/04/per-processor-licenses-for-your-application/.




Dave

VMware Communities User Moderator

Now available - vSphere Quick Start Guide

Do you have a system or PCI card working with VMDirectPath? Submit your specs to the Unofficial VMDirectPath HCL.

[andi303]

Dave,

Thanks for this very helpful answer!

Using the cpuid.corePerSocket setting did the trick.

I've successfully used this with a Win7 Pro 64bit VM.

[lowburb]

Dave

Are there any performance gains in assigning more than one of anything, whether it be vCPU's or vCORES? I read in another thread that if you stick with only one CPU, you'll get better multithreading as ESX is handling how it's dispursed across the physical CPU's. Because of that thread, I've just stayed with the default one CPU per VM, but I've also seen a lot of 100% CPU utilization in the VM task manager as I'm doing mildly CPU intensive tasks, like installing applications.