What is High-Availability Cluster?
High-availability clusters are groups of computers that support applications on server and can be reliably utilized with a minimum of down-time. These clusters operate using high availability software to harness redundant computers in groups or clusters that provide continued service when system components fail. Without clustering, if a server running a particular application crashes, the application will be unavailable until the crashed server is fixed.
HA clustering remedies this situation by detecting hardware/software faults, and immediately restarting the application on another system without requiring administrative intervention, a process known as failover. As part of this process, clustering software may configure the node before starting the application on it. High Availability clusters are used for important databases, file sharing on a network, business applications, and customer services such as electronic commerce websites.