Quorum Variations

So far we have examined what is called a strict quorum in contrast to a sloppy quorum which we’ll discuss next. Consider a system composed of several dozen nodes. It may not make sense to replicate each data value to every node so we may choose a subset of nodes in the cluster for replicating each value instead of replicating the values on every node in the cluster. Going back to our inequality R + W > N, the N in this scenario is less than the number of nodes in the cluster.

When a network partition takes place, it can happen that the chosen subset of nodes where we want to replicate a given value is not reachable partially. However, other nodes in the cluster are still reachable which aren’t designated to ...