How to calculate the MHz value required to reserve a specific percentage of CPU resources on a virtual machine (VM) with X vCPUs

Products

• VMware vSphere ESXi

Issue/Introduction

How to calculate the MHz value required to reserve a specific percentage of CPU resources on a virtual machine (VM) with X vCPUs

 

Environment

vSphere ESXi

Resolution

Here's a step-by-step breakdown of how to calculate the reserved MHz: 

1. Determine the Clock Speed of  Your Host's CPUs / Determine the total available CPU MHz of the host:

This is done by multiplying the number of physical CPU cores by the CPU clock speed (in MHz). 

2. Calculate the Total MHz Available for the VM

The total MHz available for your VM is the sum of the MHz available for each of its vCPUs.

Total MHz = Number of vCPUs × Clock speed of each vCPU

let's assume we  have 16 vCPUs, and assuming a 2.0 GHz clock speed for each vCPU:

Total MHz=16 vCPUs×2000 MHz=32,000 MHz\text{Total MHz} = 16 \, \text{vCPUs} \times 2000 \, \text{MHz} = 32,000 \, \text{MHz}Total MHz=16vCPUs×2000MHz=32,000MHz

3. Calculate 25% of the Total MHz

To reserve 25% of the total CPU resources:

Reserved MHz=Total MHz×25%=32,000 MHz×0.25=8,000 MHz\text{Reserved MHz} = \text{Total MHz} \times 25\% = 32,000 \, \text{MHz} \times 0.25 = 8,000 \, \text{MHz}Reserved MHz=Total MHz×25%=32,000MHz×0.25=8,000MHz

So, if you're reserving 25% of the CPU resources for your VM, the reservation would be 8,000 MHz.

Note: All the above numbers are based on assumptions and for example purposes only.