N+1 Redundancy
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An N+1 redundancy is a system configuration in which multiple components (N) have at least one independent backup component to ensure system functionality continues in the event of a system failure. To be at a level of N+1, the overall system integrity should not be impacted by the failure of any one component, and should continue to function at acceptable performance levels after the loss of any component.
This is different from 1+1 Redundancy, which is a system configuration whereby each critical component has a redundant backup component to ensure component-level continuity.
[edit] Applications
Redundant systems are often used in data centers to ensure that computer systems continue without service interruption. Other common implementations include aerospace, where redundant systems are used to improve safety and integrity of spacecraft, and automobiles, where the emergency brake is available in a car as a redundant component in case of failure of the main brake systems.
