# Redundancy

> A mechanism that keeps spare instances or capacity for a critical component, spread across failure domains.

Record: `architecture:redundancy`
Kind: mechanism
Layer: [Correctness Core](https://banes-lab.com/records/layer/correctness-core.md)
Severity: contextual
Scope: infrastructure, service, data
Canonical: https://banes-lab.com/ontology#architecture-redundancy

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Failover](https://banes-lab.com/records/architecture/failover.md) and before [Replication](https://banes-lab.com/records/architecture/replication.md).

## Repair

- Refactored by: Add Replica, Add Backup Path
- Detected by: SPOF analysis
- Violated by: critical singleton dependency
- Measured by: redundancy factor
- Enforced by: [architecture review](https://banes-lab.com/records/architecture/architecture-review.md)

## Requires

- [Replication or Alternate Capacity](https://banes-lab.com/records/lexicon/replication-or-alternate-capacity.md)

## Reinforces

- [Fault Tolerance](https://banes-lab.com/records/architecture/fault-tolerance.md)

## Enables

- [Failover](https://banes-lab.com/records/architecture/failover.md)

## Conflicts with

- [Single Point of Failure](https://banes-lab.com/records/lexicon/single-point-of-failure.md)

## In tension with

- [Cost](https://banes-lab.com/records/lexicon/cost.md)

## Tensions

- [Redundancy / Cost](https://banes-lab.com/records/tension/cost-redundancy.md)

## Severity

- [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md)

## Category

- [Self-Healing / Recovery / Deployment Safety](https://banes-lab.com/records/architecture-category/self-healing-recovery-deployment-safety.md)

## Reinforced by

- [RAID Redundancy](https://banes-lab.com/records/architecture/raid-redundancy.md)

## Linked from

- [Error Handling / Resilience](https://banes-lab.com/ontology/principles/architecture-category-error-handling-resilience.md)
- [Self-Healing / Recovery / Deployment Safety](https://banes-lab.com/ontology/principles/architecture-category-self-healing-recovery-deployment-safety.md)
- [Core Vocabulary](https://banes-lab.com/ontology/lexicon/lexicon-category-core-vocabulary.md)
- [Self-Healing / Recovery / Deployment Safety](https://banes-lab.com/ontology/lexicon/lexicon-category-self-healing-recovery-deployment-safety.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)