What is an 'Affinity Rule' in VMware vSphere?

An Affinity Rule in VMware vSphere is designed to ensure that specific virtual machines (VMs) are scheduled to run on the same ESXi host. This capability is particularly useful in scenarios where certain applications or services need to communicate frequently, as having them co-located on the same host can reduce latency and improve performance.

By using Affinity Rules, administrators can optimize resource usage, decrease the overhead associated with network communication between VMs, and address licensing considerations or other application-specific requirements that mandate close proximity of certain VMs. This feature plays a significant role in maintaining the performance and efficiency of distributed applications and services running within the virtualized environment.