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ashwinwriter
Contributor
Contributor

CPUs on Virtual machine when compared to physical machine

Hi there,

I have a question around CPUs on Virtual machine when compared to physical machine and how does it matter from performance perspective.

For analogy:

Physical Box     - 4 sockets x 2 Cores  = 8 Processors

Virtual Machine - 2 vCPU x 4 cores       = 8 Processors

My question is - Does it matter at the VM level, whether I select :

ESXi with 4 Sockets x 8 Cores:

1. 1 vCPU x 8 Cores

2. 2 vCPU x 4 Cores

3. 4 vCPU x 2 Cores

Would vCPU selection [In terms of socket/core]  have any impact on the Client application(s} which are CPU intensive. Are any best practices when choosing a CPU sockets/cores when converting a Physical box to VM.

Thanks for your time,

-Ashwin

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corvettefisher
Enthusiast
Enthusiast

VMware treats the execution of sockets and cores the same, the difference will come into play with licensing and how the underlying OS/Applications may handle processing based on Cores vs. Sockets.

Again you should only assign what vCPU's are needed for best performance; over allocation of too many vCPU's will actually hurt performance more so than helping it. This is due to the fact the underlying hardware might be to far over provisioned, causing contention issues.

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ashwinwriter
Contributor
Contributor

Thanks for quick reply.

Can you please elaborate more on the CPU over provision ? What exactly you mean by that. Do you mean more CPUs than actually required by VMs, or More CPUs than you actually have at Physical level. Thanks.

By the way, I just came across a excellent write up on this:[ Just reading this..]

Virtual CPUs & the Overprovisioning of vCPU to pCPU ratios

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rcporto
Leadership
Leadership

Check this blog post and test results about core per socket performance: Does corespersocket Affect Performance? | VMware vSphere Blog - VMware Blogs

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Richardson Porto
Senior Infrastructure Specialist
LinkedIn: http://linkedin.com/in/richardsonporto
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