An administrator is attempting to enable Legacy Fault Tolerance (FT) on a virtual machine and observes the
following in the vSphere Web Client:
Fault Tolerance has not been licensed on host <hostname>.
What is the minimum licensed edition that supports this configuration?

A.
Standard

B.
Enterprise

C.
Enterprise Plus

D.
Essentials Plus

Explanation:

Fault Tolerance is not licensed in all editions of VMware vSphere. Check the edition you are running and upgrade to an edition that includes Fault Tolerance.
Reference: http://kb.vmware.com/selfservice/microsites/search.do?
language=en_US&cmd=displayKC&externalId=1033634