After you create a cluster, admission control allows you to specify whether virtual machines can be started if they violate availability constraints. The cluster reserves resources to allow failover for all running virtual machines on the specified number of hosts.

The Admission Control page appears only if you enabled vSphere HA.


  1. In the vSphere Web Client, browse to the vSphere HA cluster.
  2. Click the Manage tab and click Settings.
  3. Under Settings, select vSphere HA and click Edit.
  4. Expand Admission Control to display the configuration options.
  5. Select an admission control policy to apply to the cluster.
    Option Description
    Define failover capacity by static number of hosts Select the maximum number of host failures that you can recover from or to guarantee failover for. Also, you must select a slot size policy.
    Define failover capacity by reserving a percentage of the cluster resources Specify a percentage of the cluster’s CPU and Memory resources to reserve as spare capacity to support failovers.
    Use dedicated failover hosts Select hosts to use for failover actions. Failovers can still occur to other hosts in the cluster if a default failover host does not have enough resources.
    Do not reserve failover capacity This option allows virtual machine power-ons that violate availability constraints.
  6. Click OK.


Admission control is enabled and the policy that you chose takes effect.