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

When Fault Tolerance is turned on, vCenter Server resets 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, number of vCPUs, or shares. You also cannot add or remove disks for the VM. When Fault Tolerance is turned off, any parameters that were changed are not reverted to their original values.

Connect vSphere Client to vCenter Server using an account with cluster administrator permissions.


The option to turn on Fault Tolerance is unavailable (dimmed) if any of these conditions apply:

  • The virtual machine resides on a host that does not have a license for the feature.
  • The virtual machine resides on a host that is in maintenance mode or standby mode.
  • The virtual machine is disconnected or orphaned (its .vmx file cannot be accessed).
  • The user does not have permission to turn the feature on.


  1. In the vSphere Client, browse to the virtual machine for which you want to turn on Fault Tolerance.
  2. Right-click the virtual machine and select Fault Tolerance > Turn On Fault Tolerance.
  3. Click Yes.
  4. Select a datastore on which to place the Secondary VM configuration files. Then click Next.
  5. Select a host on which to place the Secondary VM. Then click Next.
  6. Review your selections and then click Finish.


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.
Note: The VM datastores and memory are replicated during the FT Turn On process. This can take several minutes depending on the size of the replicated data. The VM state does not appear as protected until replication is complete.