What is the purpose of Idle Memory Tax in vSphere 6?

The purpose of Idle Memory Tax in vSphere 6 is to encourage active memory usage by virtual machines (VMs) by applying a form of cost or penalty for memory resources that are not being actively utilized. This mechanism is aimed at optimizing memory allocation and ensuring that resources are used efficiently across the cluster.

When the Idle Memory Tax is applied, it typically means that the hypervisor will charge more for memory that is allocated but not actively being used by a VM. This encourages the VMs to either utilize more of the memory allocated to them or to release idle memory resources back to the shared pool. As a result, this leads to better resource management and allows for more effective distribution of memory across VMs that may need it more urgently.

The concept behind the Idle Memory Tax is closely tied to the overall efficiency and resource utilization objective of virtualization environments, where it is important to maximize the use of available resources while minimizing waste. By implementing this tax, administrators can promote better performance and effective management of the memory resources within vSphere.