When vSphere High Availability (HA) has been enabled on a vSphere cluster, the virtual machines running on the cluster are protected from a host hardware failure or virtual machine guest operating system crash.
In the event that a host suffers a hardware failure or if ESXi crashes, the virtual machines are restarted on the surviving hosts in the cluster. Resources must be reserved in the cluster to guarantee that the necessary resources are available to restart the virtual machines.
Edit the settings of the vSphere cluster to enable High Availability.
Enable the HA Admission Control policy.
Select the HA Admission Control policy that should be applied to the cluster.
Define the failover settings required based on the HA Admission Control policy selected.