Chapter 4
Generalized Algorithm of Fault
Tolerance (GAFT)
Abstract Fault tolerance so far was considered as a property of a system. In fact
and instead, we introduce a Generalized Algorithm of Fault Tolerance (GAFT) that
considers property of fault tolerance as a system process. GAFT implementation
analysis—if we want to make it rigorous—should be using classification of redundancy types. Various redundancy types have different “power” of use at various
steps of GAFT. Properties of GAFT implementation impact on overall performance
of the system, coverage of faults, and ability of reconfiguration. Clear that separation of malfunctions from permanent fault simply must be implemented and
reliability gain is analyzed. A ratio of malfunctions to permanent faults is achieving
10
5−7 and simple exclusion from working configuration a malfunctioned element is
no longer feasible. Further, we have to consider GAFT extension in terms of
generalization and application for support of system safety of complex systems. Our
algorithms of searching correct state, “guilty” element, and analysis of potential
damages become powerful extension of GAFT for challenging applications like
avionic systems, aircraft as a whole. In Chap. 3, we showed that fault tolerance
should be treated as a process. In this chapter, we elaborate further this process into
a clearly defined algorithm and develop a framework to the design of fault-tolerant
systems, the generalized algorithm of fault tolerance—GAFT.We also introduce a
theoretical model to quantify the impact of the additional redundancy to the reliability of the whole system and derive an answer to the question of how much
added redundancy leads to the system with highest reliability. A question that
GAFT cannot answer is how the real source of a detected fault can be identified, as
the fault manifestation might have occurred in another hardware element and spread
in the system due to nonexistent fault containment. We will show an algorithm that
based on the dependencies of the elements of a system can identify the possible
fault sources and also predict which elements an identified fault might have
affected. We now start in a first step by further elaborating the process of fault
tolerance.
© Springer Nature Switzerland AG 2020
I. Schagaev et al., Software Design for Resilient Computer Systems,
https://doi.org/10.1007/978-3-030-21244-5_4
25
Generalized Algorithm of Fault
Tolerance (GAFT)
Abstract Fault tolerance so far was considered as a property of a system. In fact
and instead, we introduce a Generalized Algorithm of Fault Tolerance (GAFT) that
considers property of fault tolerance as a system process. GAFT implementation
analysis—if we want to make it rigorous—should be using classification of redundancy types. Various redundancy types have different “power” of use at various
steps of GAFT. Properties of GAFT implementation impact on overall performance
of the system, coverage of faults, and ability of reconfiguration. Clear that separation of malfunctions from permanent fault simply must be implemented and
reliability gain is analyzed. A ratio of malfunctions to permanent faults is achieving
10
5−7 and simple exclusion from working configuration a malfunctioned element is
no longer feasible. Further, we have to consider GAFT extension in terms of
generalization and application for support of system safety of complex systems. Our
algorithms of searching correct state, “guilty” element, and analysis of potential
damages become powerful extension of GAFT for challenging applications like
avionic systems, aircraft as a whole. In Chap. 3, we showed that fault tolerance
should be treated as a process. In this chapter, we elaborate further this process into
a clearly defined algorithm and develop a framework to the design of fault-tolerant
systems, the generalized algorithm of fault tolerance—GAFT.We also introduce a
theoretical model to quantify the impact of the additional redundancy to the reliability of the whole system and derive an answer to the question of how much
added redundancy leads to the system with highest reliability. A question that
GAFT cannot answer is how the real source of a detected fault can be identified, as
the fault manifestation might have occurred in another hardware element and spread
in the system due to nonexistent fault containment. We will show an algorithm that
based on the dependencies of the elements of a system can identify the possible
fault sources and also predict which elements an identified fault might have
affected. We now start in a first step by further elaborating the process of fault
tolerance.
© Springer Nature Switzerland AG 2020
I. Schagaev et al., Software Design for Resilient Computer Systems,
https://doi.org/10.1007/978-3-030-21244-5_4
25