VM Core vs vCPU

Question

Hello,4When we select VM SKU, there are CPU with Cores and vCPU. What diifferent between Cores and vCPU?

Answer 1

Hi @Handian Sudianto

In Azure, a virtual CPU (vCPU) equates to a core on a physical machine. When you select an Azure VM SKU, you can choose the number of vCPUs you want for your VM. The number of vCPUs you choose determines the number of cores that will be allocated to your VM.

For example, if you choose a VM SKU with 4 vCPUs, your VM will be allocated 4 cores from the physical machine. The difference between cores and vCPUs is that cores are physical processors, while vCPUs are virtual processors that are created by the hypervisor and presented to the VM as if they were physical processors.

In summary, vCPUs are the number of virtual processors that are allocated to your VM, while cores are the number of physical processors that are allocated to your VM.

About the question on performance,
The performance difference between cores and vCPUs can vary depending on the workload and the specific VM SKU you choose.

For example, some VM SKUs may have a higher clock speed or more cache per vCPU than others, which can affect performance. Additionally, some workloads may be more sensitive to the number of cores or vCPUs, while others may be more sensitive to clock speed or memory.

When choosing a VM SKU, it's important to consider your workload requirements and performance goals to determine whether cores or vCPUs are more appropriate for your needs.

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Answer 2

Hi

A core is a physical unit of a CPU. This means that the CPU provided to your VM has a "1 to 1" relationship with a physical core of the machine your VM is running on.

A virtual CPU (vCPU) is a physical central processing unit (CPU) that is assigned to a virtual machine (VM). A vCPU is a virtualised CPU rather than direct access to the physical core and most importantly, will be using hyperthreading.

Hope this helps,

Thanks

Michael Durkan

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