Red Hat Enterprise Linux implements highly available server solutions via clustering. It is important to note that cluster computing consists of three distinct branches:
Compute clustering (such as Beowulf) uses multiple machines to provide greater computing power for computationally intensive tasks. This type of clustering is not addressed by Red Hat Enterprise Linux.
High-availability (HA) clustering uses multiple machines to add an extra level of reliability for a service or group of services.
Load-balance clustering uses specialized routing techniques to dispatch traffic to a pool of servers.
Red Hat Enterprise Linux addresses the latter two types of clustering technology. Using a collection of programs to monitor the health of the systems and services in the cluster.
The clustering technology included in Red Hat Enterprise Linux is not synonymous with fault tolerance. Fault tolerant systems use highly specialized and often very expensive hardware to implement a fully redundant environment in which services can run uninterrupted by hardware failures.
However, fault tolerant systems do not account for operator and software errors which Red Hat Enterprise Linux can address through service redundancy. Also, since Red Hat Enterprise Linux is designed to run on commodity hardware, it creates an environment with a high level of system availability at a fraction of the cost of fault tolerant hardware.