Fault Tolerance Essay

DATA STRUCTURES

What is Fault-tolerant system
Fault-tolerance or graceful degradation is the property that enables a system (often computer-based) to continue operating properly in the event of the failure of (or one or more faults within) some of its components. Fault-tolerance is particularly sought-after in high-availability or life-critical systems.
Fault tolerance requirements:
The basic characteristics of fault tolerance require:
• No single point of repair
• Fault isolation to the failing component
• Fault containment to prevent propagation of the failure
• Availability of reversion modes
Fault-tolerance by replication
Spare components address the first fundamental characteristic of fault-tolerance in three ways:
• Replication: Providing multiple identical instances of the same system or subsystem, directing tasks or requests to all of them in parallel, and choosing the correct result on the basis of a quorum;
• Redundancy: Providing multiple identical instances of the same system and switching to one of the remaining instances in case of a failure.
• Diversity: Providing multiple different implementations of the same specification, and using them like replicated systems to cope with errors in a specific implementation.
Fault-tolerant design
In engineering, fault-tolerant design, also known as fail-safe design, is a design that enables a system to continue operation, possibly at a reduced level (also known as graceful degradation), rather than failing completely, when some part of the system fails.
When to use
Providing fault-tolerant design for every component is normally not an option. In such cases the following criteria may be used to determine which components should be fault-tolerant:
• How critical is the component? In a car, the radio is not critical, so this component has less need for fault-tolerance.
• How likely is the