Assign vCPU cores

[DespicableYO]

Hi, I am new to VMWare. I have a Dell T440 Dual Socket supported Server with Single 8Core/16Thread Xeon Processor. I want to assign the maximum number of CPUs to a single machine. I read somewhere that one core equals approximately two vCPU, which means I can assign up to 16 vCPUs. But I am not sure about it. Can you please suggest, how much maximum number of CPUs that I can assign to my single VM with 8C/16T processor.

[IRIX201110141 · Accepted solution]

Your 8 cores together with Hypertreading gives 16 HEC(hardware execution context) where a VMM (virtual machine monitor) can be placed which ends up to 16 logical CPU.

• So you can create a VM with up to 16 vCPUs
• You can create and (technically) run multiple 16 vCPUs VMs
• Choose N vCores and 1 Socket
• There is no performance difference betwwen vCores or vSockets. It have to do with license within the GuestOS. A windows Guest OS only supports 2 Sockets for example
• HT gives not the double performance. In larger farms it gives up to 23 percent more performance and it depends on the application
• The ESXi needs a little bit CPU also. So assign not all available vCPU to your one VM

In short... there is no big difference between a OS installation on bar metal compared to a VM on a hypervisor on your single Host.

Best practices is only to assign these resources to a VM which can be allocated and use by the Application/Workload and not more.

Regards,

Joerg

[scott28tt]

Regardless of how many you can allocate as a maximum, best practice is usually to allocate as few as possible to achieve the desired level of performance. How many vCPU cores does the workload in your VM NEED?

Bear in mind also that hyper threading doesn’t usually double performance, in other words you may find that once the number of vCPU cores is above 8 (in your case) that performance doesn’t continue to increase as you might expect.