Simplex is designed to support the evolution of mission-critical systems that have high availability or reliability requirements. Its suitability for management information systems (e.g., MIS) applications that do not have such requirements has yet to be determined. Its usefulness in C4I systems is currently being investigated.
Although Simplex has been designed to reduce the life-cycle cost of systems, data on its impact on system life-cycle cost is not available at this time. Much of Simplex is built upon COTS components such as a POSIX compliant real-time operating system running on modern hardware. This tends to reduce costs relative to custom designs.
When using Simplex, engineering costs are increased by the need to analyze and create the analytically redundant modules. Additionally, there is some overhead involved in the operation of the monitoring and switching logic. Finally, the need to run multiple copies of an application (i.e., the HRC and HPC simultaneously) requires additional resources-at the very least additional memory and CPU cycles. These factors tend to have an upward effect on costs-compensated for by the increased reliability and flexibility which Simplex provides.
A perhaps more important consideration is the savings that Simplex provides by reducing the required testing and downtime when installing an upgraded component. The expectation is that the use of Simplex will provide a significant savings in total life-cycle cost.
Software and hardware reliability modeling and analysis allow users to estimate the impact of Simplex on system reliability. System life-cycle cost estimation techniques will allow users to estimate the cost impact.
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