A cluster is a group of independent computers working together as a single system to ensure that mission-critical applications and resources are highly available. The cluster is managed as a single system, shares a common namespace, and is specifically designed to tolerate component failures and to support the addition or removal of components in a way that is transparent to users.

Keeping data and applications functioning 24 hours day and seven days a week is a requirement for critical applications today. Clustered systems have several advantages, including fault tolerance, high availability, scalability, simplified management, and support for rolling upgrades.