In order to ensure data consistency across complete restarts, a quorum of servers is required. A quorum is ½ cluster size + 1. This is the minimum number of nodes to ensure at least one node has the most recent data and state after a catastrophic failure. So for a cluster size of 3, you’ll need at least two JetStream enabled NATS servers available to store new messages. For a cluster size of 5, you’ll need at least 3 NATS servers, and so forth.