Now that we have created a cluster to house all our data, with a number of nodes holding both owned partitions and backups; but what happens if we need to scale? This could be for a number of reasons, for example, approaching the current memory capacity or our application is rather demanding and saturating a hardware resource. The solution in both cases is simple; add more nodes.

So if we were to start with a cluster of four nodes holding overall 4 million objects, each individual node would hold roughly 1 million owned objects (and a further 1 million backups). When we introduce a new node, Hazelcast reacts by assigning partitions from existing nodes to it. This will cause existing data to stream across to the new node taking on more and more partitions until it holds an overall fair share. The net result will be that each node now only holds approximately 8,00,000 owned objects (and a similar number of backups). In adding this new node we have created additional capacity...