Clustered hosting : High Availability clusters
Clustered hosting is a type of Web hosting that spreads the amount of hosting across multiple physical machines, thus increasing availability. Many large websites run on clustered hosting solutions.
Most hosting infrastructures are based on the exemplar of using a single physical machine to host multiple services, including email, web, database, FTP and others. A single physical machine is not only a single point of failure, but also has definite capacity for traffic.
By clustering services over multiple hardware machines and using load balancing, single points of failure can be removed. A single server can depend upon periodic reboots for software upgrades whereas in a clustered platform you can stagger the restarts such that the service is still available while still upgrading all necessary machines in the cluster.
Clustered hosting is same as cloud hosting in the way that the resources of many machines are available for a website to apply on demand.
High-availability clusters are groups of computers that support server applications which can be reliably utilized with a reduced time. In the absence of clustering, if a server running a particular application crashes, the application will be unaccessible until the crashed server is fixed. HA clustering solves this situation by detecting hardware/software errors, and immediately restarting the application on another system.
HA clusters are used for critical databases, business applications, file sharing on a network, and customer services such as electronic commerce websites.