Rack Fault Tolerance is the ability to provide rack level availability domain. With rack fault tolerance, redundant copies of data are made and placed on the nodes that are not in the same rack. When rack fault tolerance is enabled, the cluster has rack awareness and the guest VMs can continue to run with failure of one rack (RF2) or two racks (RF3). The redundant copies of guest VM data and metadata exist on other racks when one rack fails.
Nutanix, ECP [HCI]/5.11, Starter
Rack Failure Protection, Reads/Writes, Data Availability