Fault Tolerance

Definition - What does Fault Tolerance mean?

Fault tolerance is the way in which an operating system (OS) responds to a hardware or software failure. The term essentially refers to a system’s ability to allow for failures or malfunctions, and this ability may be provided by software, hardware or a combination of both. To handle faults gracefully, some computer systems have two or more duplicate systems.

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Techopedia explains Fault Tolerance

Fault tolerance software may be part of the OS interface, allowing the programmer to check critical data at specific points during a transaction.

Fault tolerance can include:

Responding to a power failure (the lowest level of fault tolerance)
Immediately using a backup system in the event of a system failure
Allowing mirrored disks to immediately take over for a failed disk
Multiple processors working together and comparing data and output for errors, then immediately correcting the detected errors.

In general, 100% fault tolerance can never be achieved due to cost constraints.