Understanding vSphere Virtual Machine (VM) Overhead Memory Calculation and Fluctuation

Products

• VMware vCenter Server

Issue/Introduction

Does a virtual machine's overhead memory reservation value fluctuate between its power-on state and its running state ?

 

Environment

VMware vSphere ESXi

VMware vCenter Server

Resolution

The overhead memory reservation required for a virtual machine is calculated by the system when the VM is powered on. This calculation is based on the VM's specific configuration, primarily the number of vCPUs and the configured memory size.

As a general rule, this overhead value does not fluctuate after the VM is powered on. The only exception is if the VM's configuration is modified while it is running (e.g., performing a vCPU Hot-Add). In such cases, the overhead memory reservation will be recalculated.

For detailed information on how memory resources and overhead are managed and calculated, please refer to the official vSphere resource management documentation.

Understanding Memory Overhead