Clustering
Clustering involves linking a group of computers closely together to act in unison. Clustering has been used for more than 20 years by large organizations to increase computing power, improve response times, and provide continuous operation despite failed hardware or applications. Enterprise solutions rely heavily on clustering to keep up performance and reliability for hundreds and thousands of users.
In recent years, the increase in virtualization and performance improvements in hardware and software have contributed to a much wider deployment of clustering. Many hardware and software solutions that could not use this functionality in the past are being built to work in a clustered environment.
High-availability (HA) clusters are implemented primarily for redundacy to allow for critical applications to continue on a different server if the primary server fails. HA cluster implementations attempt to use redundancy of cluster components to eliminate single points of failure.