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Chapter 9. Safety and Reliability Patterns > Homogeneous Redundancy Pattern

9.3. Homogeneous Redundancy Pattern

The Homogeneous Redundancy Pattern is primarily a pattern to improve reliability by offering multiple channels. These channels can operate in sequence, as in the Switch To Backup Pattern (another name for this pattern), or in parallel, as in the Triple Modular Redundancy Pattern, described later. The pattern improves reliability by addressing random faults (failures). Since the redundancy is homogeneous, by definition any systematic fault in one copy of the system is replicated in its clones, so it provides no protection against systematic faults (errors).

9.3.1. Abstract

An obvious approach to solving the problem of things breaking is to provide multiple copies of that thing. In safety and reliability architectures, the fundamental unit is called a channel. A channel is a kind of subsystem, or run-time organizational unit, which is end-to-end in its scope, from the monitoring of real-world signals to the control of actuators that do the work of the system. The Homogeneous Redundancy Pattern replicates channels with a switch-to-backup policy in the case of an error.


  

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