The number of virtual machine vCPUs allocated compared to the number of physical CPU cores available is the vCPU-to-core ratio. Determining this ratio will depend on the CPU utilization of the workloads.
If the workloads are CPU-intensive, the vCPU-to-core ratio will need to be smaller; if the workloads are not CPU-intensive, the vCPU-to-core ratio can be larger. A typical vCPU-to-core ratio for server workloads is about 4:1—four vCPUs allocated for each available physical core. However, this can be much higher if workloads are not CPU-intensive.
A vCPU-to-core ratio that is too large can result in high CPU ready times—the percentage of time that a virtual machine is ready but is unable to be scheduled to run on the physical CPU—which will have a negative impact on the virtual machine's performance.
