What is difference between Fault Tolerance and Fault Resilience?

Fault tolerance and fault resilience are closely related concepts in software architecture, often used interchangeably, but they have distinct meanings and implications for system design.

Fault Tolerance

Fault tolerance refers to the ability of a system to continue operating properly in the event of a failure of some of its components. This concept is primarily about the system's capacity to endure faults without interrupting the overall functionality. It involves mechanisms that allow the system to continue its operations at a reduced level of performance without any downtime for the user. Common strategies for achieving fault tolerance include redundancy, where multiple instances of a component are run to ensure that if one fails, others can take over seamlessly. This approach ensures that users do not experience any service disruption, even if some components of the system fail[1][2][3].

Fault Resilience

Fault resilience, on the other hand, is about the system's ability to recover quickly and effectively from a fault or failure. While fault tolerance is about prevention, fault resilience is more about recovery. It involves the system's capacity to handle and eventually recover from unexpected conditions. This might mean that when a fault occurs, some level of service degradation is acceptable temporarily, but the system can restore full functionality on its own without manual intervention. Techniques such as state checkpoints and rollback mechanisms are often used to enhance fault resilience, allowing the system to revert to a known go...