Cluster Basics
In general, computers that are connected in a cluster network are called nodes. A computer cluster is a group of two or more nodes, operating in parallel to achieve a shared goal. This allows the distribution of workloads among the nodes in the cluster. Each workload can consist of many parallelized individual tasks. A network of high-performance nodes can then solve these tasks, which in turn combine their memory and processing power.
A cluster characteristic is that all participating nodes exchange information. The computer cluster software used to join the nodes together assures internode communication. The cluster is built in such a way that it can have a shared storage device or local storage on each node, or either.
Clusters are used for different types of tasks. There are high availability clusters, load-balancing clusters, storage clusters, and high-performance clusters. In the local data center, for example, the load balancing cluster and the high availability cluster play an important role. High-availability clusters are generally used to increase fail-safety. Also, a cluster can be more than one type. It is common that a cluster hosting a web server provides high availability and is load balancing at the same time.