You can turn on vSphere Fault Tolerance through the vSphere Client.

When Fault Tolerance is turned on, vCenter Server unsets the virtual machine's memory limit and sets the memory reservation to the memory size of the virtual machine. While Fault Tolerance remains turned on, you cannot change the memory reservation, size, limit, or shares. When Fault Tolerance is turned off, any parameters that were changed are not reverted to their original values.


Open a vSphere Client connection to a to vCenter Server using an account with cluster administrator permissions.


  1. Select the Hosts & Clusters view.
  2. Right-click a single virtual machine and select Fault Tolerance > Turn On Fault Tolerance.
    If you select more than one virtual machine, the Fault Tolerance menu is disabled. You must turn Fault Tolerance on for one virtual machine at a time.


The specified virtual machine is designated as a Primary VM and a Secondary VM is established on another host. The Primary VM is now fault tolerant.