Vertica provides quite an elastic cluster, which can be scaled both up (adding new nodes) and down (removing nodes) without affecting the processes of the running database. The most important task after alteration in a cluster is the rebalancing of data across new as well as old nodes. This is done to ensure that the data remains K-Safe. Please refer to Chapter 5, Performance Improvement, for more information on K-Safe.
Projections are divided into segments, which are small portions of data. After adding a new node, some segments are given to it, while the other segments are exchanged to ensure proper K-safety. During the process of node removal from a cluster, all of the storage containers, which are residing at the node that is being removed, are moved to other existing nodes in the cluster. This method of partitioning data into movable segments turns a Vertica cluster into an elastic cluster.