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Optimizing Fault-Tolerant Systems through Version Sequencing

This study analyzes the impact of sequencing versions in fault-tolerant systems to optimize reliability and performance. It explores running software on different hardware blocks and examines parallel execution versus consecutive execution. The research delves into the characteristics of system reliability, computational resource distribution, and the effect of sequencing on system performance.

rigel-burris
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Optimizing Fault-Tolerant Systems through Version Sequencing

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  1. Hardware Software Input ? Success Failure Output

  2. Fault-Tolerant Programming N-Version Programming Recovery Blocks Scheme + Correct Result Version 1 AT - Version 1 M Identical Outputs + Correct Result Version 2 AT Version 2 Correct Result Voter - … … + Version N Failure Correct Result Version N AT - Failure

  3. N-Version Programming Parallel Execution of Versions Consecutive Execution of Versions t1 t2 t1 t2 t3 t4 t5 t3 M=3 t4 t5 T T failure success voting

  4. Fault-Tolerant System Structure Software Running on Different Hardware Blocks Software Running on Single Hardware Block … … …

  5. Effect of Parallel Versions Execution 1 3 1 2 3 4 5 2 4 5 t1+t2+t3+t4 t1+t3 L=1 L=2 1 5 1 4 1 2 2 2 5 3 3 3 4 4 5 t1+t4 t3 t3 L=3 L=4 L=5

  6. Reliability/Performance Analysis Problem Characteristics of Version Characteristics of System Reliability Reliability Pr{ T < T* } Expected Execution Time E(T) Execution Time Conditional Expected Execution Time E(T) | T < T* Computational Resources

  7. Distributionof System Execution Time Q(k/n)=Pr{ k out of n first versions succeed } i1: {1…n-k+1} i2: {i1+1…n-k+2} Pj=Pr{ system succeeds after execution of version j } = rj Q(M-1/j-1)

  8. j first versions: UGF Approach Single version i: For j = M: PM Pj Pj-1

  9. For the entire system: UGF Approach For each component c: PcM , PcM+1 ,…, Pcn TcM , TcM+1 ,…, Tcn

  10. Effect of Versions Sequencing 3-out-of-5 system 5 3 1 3 4 2 2 4 5 1 t2+t4+t5 t1+t3 5 3 3 4 4 2 1 2 5 1 t1+t2+t5 t3+t4

  11. M=1 M=2 M=3 M=2 M=1 Parameters of Software System

  12. Optimal Version Sequences

  13. T* Software Structure Optimization R(T*) MAX |C < C*

  14. Optimal Fault-Tolerant System Structures

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