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High availability clusters are designed to minimize downtime and provide uninterrupted service when nodes fail. Nodes in a highly available cluster must have access to a shared storage. Such systems are often used for failover and backup purposes. Without clustering the nodes if the server running an application goes down, the application will not be available until the server is up again. In a highly available cluster, if a node becomes inoperative, continuous service is provided by failing over service from the inoperative cluster node to another, without administrative intervention. Such clusters must maintain data integrity while failing over the service from one cluster node to another. High availability systems consist of several nodes that communicate with each other and share information. High availability makes the system highly fault tolerant with many redundant nodes, which sustain faults and failures. Such systems also ensure high reliability and scalability. The higher the redundancy, the higher the availability. A highly available system eliminates single point of failures.

Highly available systems are essential for an organization that has to protect its business against loss of transactional data or incomplete data and overcome the risk of system outage. These risks, under certain circumstances, are bound to cause millions of dollars of losses to the business. Certain applications such as online platforms may face sudden increase in traffic. To manage these traffic spikes a robust solution such as cluster computing is required. Billing, banking, and e‐commerce demand a system that is highly available with zero loss of transactional data.