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The concept of a cluster is that the cluster itself appears on the outside as a single system. A cluster consists of two or more Real Computers referred to as nodes or members of a cluster. The components of a cluster are commonly, but not always, connected to each other through fast Local Area Networks.
Clusters are usually deployed to improve performance and/or availability over that provided by a single computer, while typically being much more cost-effective than single computers of comparable speed or availability. Clustering is all about the back-end operations being performed by the nodes or members which appear to the outside world as a single computational entity.
High Performance Clusters (HPC)
Multiple nodes in cluster perform concurrent calculations. There are two key benefits of High
Performance (or grid) computing :
High Availabilty Clusters (HA)
High-availability clusters provide continuous availability of services by eliminating single points of failure and by failing over services from one cluster node to another in case a node becomes inoperative. High-availability clusters are sometimes referred to as failover clusters.
Red Hat Cluster Suite provides high-availability clustering through its High-availability
Service Management component.
Load Balancing Clusters
Load Balancing Clusters operate by having all workload come through one or more load balancing front-ends, which then distribute it to a collection of back end servers. If a node in a load-balancing cluster becomes inoperative, the load balancing software detects the failure and redirects requests to other cluster nodes. Red Hat Cluster Suite provides load- balancing through LVS (Linux Virtual Server).
Storage clusters provide a consistent file system image across servers in a cluster, allowing the servers to simultaneously read and write to a single shared file system. With a cluster-wide file system, a storage cluster eliminates the need for redundant copies of application data and simplifies backup and disaster recovery. Red Hat Cluster Suite provides storage clustering through Red Hat GFS(Global File System).