The process of distributing documents across the nodes in the cluster is called rebalancing.

As an administrators, we need to expand the cluster size by adding nodes to a cluster whenever there are resource constraints due to increases in the application load. Sometimes, we need to trim the resources of the cluster, for example, removing nodes for upgrades of software, hardware maintenance, and so on. Whenever there is a change in cluster resources, the administrator needs to perform balancing of data across the nodes. This is a deliberate process that needs to be done manually by the administrator. In Couchbase, data is distributed across nodes using the vBucket structure. During the rebalancing process, the documents stored in the vBuckets are redistributed among the nodes available at the time of the process to reflect the actual resources of the cluster.

This is an online activity; that is, the Couchbase cluster will be running and serving the clients requests during rebalancing...