Any mechanism or technology that allows a computer or operating system to recover from a failure. In fault tolerant systems, the data remains available when one component of the system fails. Here are some examples of fault tolerant systems:
Just because your system is fault tolerant doesn’t mean you are fully prepared for disaster. You still need to perform regular backups of important data. For example, a RAID 5 disk system will protect against data loss if one disk drive fails, but not if two or more drives fail simultaneously.