The New Cluster wizard allows you to enable or disable admission control for the vSphere HA cluster and choose a policy for how it is enforced.

You can enable or disable admission control for the vSphere HA cluster.

Enable: Disallow VM power on operations that violate availability constraints

Enables admission control and enforces availability constraints and preserves failover capacity. Any operation on a virtual machine that decreases the unreserved resources in the cluster and violates availability constraints is not permitted.

Disable: Allow VM power on operations that violate availability constraints

Disables admission control. Virtual machines can, for example, be powered on even if that causes insufficient failover capacity. When you do this, no warnings are presented, and the cluster does not turn red. If a cluster has insufficient failover capacity, vSphere HA can still perform failovers and it uses the VM Restart Priority setting to determine which virtual machines to power on first.

vSphere HA provides three policies for enforcing admission control, if it is enabled.

Host failures the cluster tolerates

Percentage of cluster resources reserved as failover spare capacity

Specify failover hosts

Note

See Choosing an Admission Control Policy for more information about how vSphere HA admission control works.