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What Is It?

A computer cluster is a group of loosely coupled computers (nodes) that can be viewed as a single computer. These computers often are connected to each other through dedicated networks such as LANs (Local Area Networks), and each connected computer usually is the same or similar type of machine. All connected machines usually share resources such as a common home directory. Clusters usually are built or deployed to improve performance over a single computer while being more cost effective than single computers of similar speed or availability.

Clusters also are known as a Web server farm, a Web farm, Network of Workstations (NOW), distributed system, or parallel system; however, the term, “cluster,” is used broadly when in reference to computer networking, and it’s important to recognize that network clustering involves a long history of research and development that represents many variations on the theme of computer clusters.

Who Is it For?

Computer clusters can be built by individuals at home, as the set up is basic. The cluster builder can find many tutorials online that explain computer clusters and how to build them. The individual may want to build a cluster for gaming or some other activity that requires several users and the advantage of networking those users’ computers.

Beyond this use, larger businesses and organizations such as colleges, corporations, and libraries may desire computer clusters for regulating overall compliance to policies. The computer cluster allows this boundary as each computer would comply with the same signals and programs.

Features

The true advantage to clusters comes with what is known as “high-availability (HA) clusters,” or clusters known for their ability to provide service when system components fail. Generally, an HA cluster is composed of two or more redundant nodes that eliminate single points of failure. This type of cluster feature is popular for Web hosting, as the ability to keep cluster performance at peak levels is one way to lure potential customers to a Web hosting service.

On the other hand, HA clusters are not grid clusters, as grids connect collections of computers which don’t fully trust each other or are geographically dispersed. HA clusters, as with traditional clusters, “trust” each other. In other words, traditional computer clusters share the same security, so that when a user turns one computer on the other computers respond equally. Additionally, traditional computer clusters typically are located in one room or geographic location.

Another feature provided by clusters include load-balancing clusters where the workload comes through one or more load-balancing front ends and is then distributed to other nodes on a ‘back end’ platform.

Compatibility

GNU/Linux world users support various cluster software packages for application clustering, director-based clusters, for automatic process migration among homogeneous nodes, and for single-system image implementations. Microsoft also provides cluster server products that are based on their Windows Server platform. Users who want to create clusters might research how and why they want to use them to learn more about the software and hardware designed for any given computer cluster purpose.

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