Configuring vSphere HA admission control

A well-configured HA cluster will have enough free resources to restart all of the business-critical VMs running on the hosts, in the event of host failures. This amount of free resources is referred to as the failover capacity.

Failover capacity determines the number of the ESXi hosts that can fail in an HA cluster, and still leave enough resources to support all of the powered-on VMs. We can use admission control to control and monitor the failover capacity.

There are three admission control methods (policies):

• Define the failover capacity by reserving a static number of hosts

• Define the failover capacity by reserving a percentage of the cluster resources

• Specify dedicated failover hosts

Note

Note that admission control can be disabled by selecting the Do not reserve failover capacity option.

Any operation that violates the resource constraints imposed by the admission control policy will not be permitted. Some of these operations include a VM power-on...