An administrator wants to change from Redundancy Factor 2 to 3, but it is not allowed. What must the administrator check?

Redundancy Factor 3 (RF3) is a data protection mechanism that maintains three copies of data across a Nutanix cluster, allowing it to tolerate the simultaneous failure of any two nodes or disks. To achieve this level of resilience and maintain a quorum for metadata operations, a Nutanix cluster must have a minimum of five nodes. If the cluster has fewer than five nodes, the option to change the Redundancy Factor to 3 will be unavailable or greyed out in the Prism interface, as the architectural prerequisite is not met.

A. Check that the cluster has been properly licensed. Redundancy Factor is a core feature of the Nutanix architecture and is available in all license tiers (Starter, Pro, and Ultimate). It is not a feature restricted by licensing.
C. Check hardware availability of the nodes. While nodes must be healthy for the change to complete successfully, a temporary hardware issue would likely cause the task to fail, not prevent the option from being selected in the first place.
D. Check AOS version and upgrade, if needed. RF3 has been a standard feature in AOS for many years. It is highly unlikely that a cluster would be running a version so old that it does not support RF3, making the node count the primary prerequisite.

1. Nutanix Prism Web Console Guide (AOS 6.5): In the section Modifying Cluster Details > Increasing the Cluster Redundancy Factor, the documentation states, "To change the redundancy factor to 3, the cluster must have at least five nodes."

2. Nutanix University - Nutanix Hybrid Cloud Fundamentals Courseware: In the module Data Resiliency, the course material explains that for a Fault Tolerance level of 2 (achieved with RF3), a minimum of 5 nodes are required. This is based on the 2n+1 formula for quorum, where n is the number of failures to tolerate.

3. Nutanix Data Protection and Recovery Guide (AOS 6.5): Under the section Data-at-Rest Resiliency > Redundancy Factor, it is specified that "Redundancy factor 3 requires that the cluster has at least five nodes."