> oh i know you can run rf 3 on a 3 node cluster. more i thought that if you > have one fail you have less nodes than the rf, so the cluster is at less > than rf, and writes might be disabled or something like that, while at 4 you > still have met the rf...
A node failing is independent of RF. *Decommissioning* a node from the ring would be a problem however. But replacing it with a new node would not. Unless administrative actions in terms of moving or adding nodes to the ring happen, data is never copied to nodes that are not supposed to be responsible for it. If a node is down in a cluster with RF=3, then for whatever ranges of the ring that node was partially responsible for, only 2 of the 3 copies will be up/available. They do not automatically migrate somewhere else. -- / Peter Schuller (@scode on twitter)
