As noted earlier, a cluster consists of a set of one or more nodes, all running grb_rs. This section explains how to form a cluster. Multi-node clusters provide additional capabilities relative to single-node clusters. For Compute Server, a multi-node cluster will automatically balance computational load among the various member nodes. For distributed algorithms, a multi-node cluster enables various algorithms to distribute work among multiple machines. This section begins by discussing the different types of nodes that are needed to support both Compute Server and distributed algorithms. Next, we will explain the grouping feature that can be used to create subsets of nodes to process some jobs. Finally, we will discuss the dynamic nature of a cluster. The system administrator can ask individual nodes to start or stop processing jobs, which makes it possible to smoothly add or remove nodes from a cluster to simplify maintenance or to scale processing capacity up or down.