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An experimental evaluation of software redundancy as a strategy for improving reliabilityThe strategy of using multiple versions of independently developed software as a means to tolerate residual software design faults is suggested by the success of hardware redundancy for tolerating hardware failures. Although, as generally accepted, the independence of hardware failures resulting from physical wearout can lead to substantial increases in reliability for redundant hardware structures, a similar conclusion is not immediate for software. The degree to which design faults are manifested as independent failures determines the effectiveness of redundancy as a method for improving software reliability. Interest in multi-version software centers on whether it provides an adequate measure of increased reliability to warrant its use in critical applications. The effectiveness of multi-version software is studied by comparing estimates of the failure probabilities of these systems with the failure probabilities of single versions. The estimates are obtained under a model of dependent failures and compared with estimates obtained when failures are assumed to be independent. The experimental results are based on twenty versions of an aerospace application developed and certified by sixty programmers from four universities. Descriptions of the application, development and certification processes, and operational evaluation are given together with an analysis of the twenty versions.
Document ID
19900014642
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Eckhardt, Dave E., Jr. (NASA Langley Research Center Hampton, VA., United States)
Caglayan, Alper K. (NASA Langley Research Center Hampton, VA., United States)
Knight, John C. (NASA Langley Research Center Hampton, VA., United States)
Lee, Larry D. (NASA Langley Research Center Hampton, VA., United States)
Mcallister, David F. (NASA Langley Research Center Hampton, VA., United States)
Vouk, Mladen A. (NASA Langley Research Center Hampton, VA., United States)
Kelly, John P. J. (California Univ. Santa Barbara., United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1990
Subject Category
Computer Programming And Software
Report/Patent Number
NAS 1.15:102613
NASA-TM-102613
Accession Number
90N23958
Funding Number(s)
PROJECT: RTOP 505-65-11
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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