RF3 Compliance Requirement on a Five-Node Cluster
A five-node NX-8035-G7 cluster has 6 TB raw SSD per node and currently runs all containers at RF2. Prism shows 11.8 TB logical used across 220 VMs. A compliance audit now requires the production container to survive two simultaneous node failures. The customer proposes changing the production container from RF2 to RF3 without adding hardware, arguing that five nodes already exceed the three-node minimum. The cluster has 18% free space, and the customer cannot accept a write outage. The production container holds 9.5 TB of the used capacity; the remaining 2.3 TB is on a dev container that can stay at RF2. Node CPU is 55% busy at peak, and the network is 25 GbE.
1. Evaluate whether RF3 can be enabled on the existing five nodes without adding capacity.
Read the worked answer
Supportability is not the constraint; capacity is. Raw capacity is 5 × 6 TB = 30 TB. With RF2, usable capacity is about 15 TB, minus reserve; 11.8 TB used is already roughly 79% of that. Moving only the production container to RF3 means its 9.5 TB needs about 28.5 TB of raw space. The dev container at RF2 still needs about 4.6 TB raw. Total raw demand is about 33.1 TB before reserve, which already exceeds 30 TB. Therefore RF3 cannot be enabled safely without adding capacity or reducing data. Adding one 6 TB node gives 36 TB raw, leaving only about 2.9 TB before reserve, which is too tight for rebuilds and snapshots. Two additional nodes, or a substantial reduction in production data, are required.
2. What is the operational risk of changing RF on a live container, and how would you sequence it?
Read the worked answer
Changing RF triggers replication of existing data and a large background workload. It does not normally require a write outage, but it can significantly increase IO, CPU, and network utilization, and it needs free capacity for the new replicas. Before starting, confirm all nodes are healthy, no rebuild is active, NCC is clean, and capacity is comfortably above thresholds. Schedule a window and monitor resiliency and latency during the change. Do not start the RF change while another node is down. After the change, verify the container reports RF3 in Prism and CLI, confirm all VMs remain accessible, and wait for full resiliency before any further maintenance. If capacity is insufficient, the change may stall or fill the cluster; fix capacity first rather than forcing the setting.
3. How does RF3 change failure tolerance during maintenance?
Read the worked answer
RF3 keeps three copies of data, so the cluster can tolerate two simultaneous failures without losing availability. With five nodes, taking one node down for maintenance leaves four nodes and still allows one more failure; the data remains available. However, after a failure, rebuild activity can temporarily reduce performance and capacity headroom, so maintenance should still be performed one node at a time. Verify that resiliency has returned to a healthy state before taking the next node down. RF3 also increases raw capacity consumption, so any maintenance plan must account for the reduced free space during rebuild.