On reconfiguration latency in fault-tolerant system

Digital computers embedded in critical applications such as flight controls should be equipped with appropriate fault-tolerance schemes to ensure their reliable and safe operation in the presence of component failures. System reconfiguration, which enhances reliability by dynamically using spatial redundancy, is generally the most time-consuming fault-/error- handling stage. The reconfiguration latency, defined as the time taken for reconfiguring a system upon failure detection or mode change, depends on many parameters, including the size of application programs and data, the CPU and memory speed, built-in testing capabilities, the type of spares to use, the system architecture, and the reconfiguration strategy used. In this paper, we classify the reconfiguration techniques into four types: reconfigurable duplication, reconfigurable N-modular redundancy (NMR), backup sparing, and graceful degradation. For each type of reconfiguration, we evaluate the reconfiguration latency by using several parameters accounting for the aforementioned parameters, and determine if this type of reconfiguration can meet the application required latency.<
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