hardware clustering

What is hardware clustering?

Hardware clustering, sometimes called operating system (OS) clustering, is a hardware-based method of turning multiple servers into a cluster -- a group of servers that acts like a single system.

As a rule, a hardware cluster is created by installing a number of blade servers on the machine that controls the cluster. Each blade server functions independently of the others, although they all respond to the same requests. The OS of the controlling server monitors the cluster and performs administrative tasks, such as deciding when failover is necessary and assigning the load of a failed node to a functioning server.

A hardware cluster may be active-passive, in which case some redundant servers are reserved for failover duty and do not run any applications of their own. It can also be active-active, in which case all servers in the cluster run their own applications but also reserve resources to enable them to perform failover duty for each other.

Hardware clustering requires software application changes. The alternative to hardware clustering, application clustering, is a software-based method of clustering servers. Because application clustering doesn't require specialized hardware, it is usually less expensive to implement than hardware clustering.