To ensure optimal VMware HA cluster performance, VMware recommends that you follow certain best practices. Networking configuration and redundancy are important when designing and implementing your cluster.

When VMware HA or Fault Tolerance take action to maintain availability, for example, a virtual machine failover, you might need to be notified about such changes. You can configure alarms in vCenter Server to be triggered when these actions are taken, and have alerts, such as emails, sent to a specified set of administrators.

A valid cluster is one in which the admission control policy has not been violated.

A cluster enabled for VMware HA becomes invalid (red) when the number of virtual machines powered on exceeds the failover requirements, that is, the current failover capacity is smaller than configured failover capacity. If admission control is disabled, clusters do not become invalid.

The cluster's Summary page in the vSphere Client displays a list of configuration issues for clusters. The list explains what has caused the cluster to become invalid or overcommitted (yellow).

DRS behavior is not affected if a cluster is red because of a VMware HA issue.

Configuration issues and other errors can occur for your cluster or its hosts that adversely affect the proper operation of VMware HA. You can monitor these errors by looking at the Cluster Operational Status screen, which is accessible in the vSphere Client from the VMware HA section of the cluster's Summary tab. You should address any issues listed here.