What configuration change can ensure an RF2 cluster survives a complete rack failure?

To ensure that a replication factor of 2 (RF2) cluster can survive a complete rack failure, it's essential to distribute the nodes across multiple racks effectively. RF2 means that each piece of data is stored in two different locations, which typically implies that there should be at least two copies of data on two separate racks for redundancy.

By adding 3 additional nodes per rack in a scenario where you already have a certain number of nodes, you not only increase the total number of nodes, but also maintain data redundancy across racks. Thus, if one complete rack fails, the data can still be accessed from another rack, ensuring high availability. In this case, with a configuration that adds 3 nodes to each of 3 racks (resulting in 9 additional nodes total across the racks), the overall resilience of the cluster increases as it can accommodate rack failures without losing data.

This configuration balances the distribution of replicas effectively and provides greater fault tolerance within the cluster, allowing it to survive complete rack failures without jeopardizing data availability.