Lecture15 - previous figure Mission time, in units of MTTF...

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Click to edit Master subtitle style 5/13/10 Lecture 6 COP 5611 Operating Systems Spring 2010 Dan C. Marinescu Office: HEC 439 B Office hours: M-Wd 1:00-2:00 PM
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5/13/10 22 2 Lecture 15 n Reading Assignment: Chapter 9 from the online textbook n Homework 3 due today. Midterm: Wednesday March 17 n Last time: ¨ Coding ¨ Replication ¨ Voting n Today: ¨ Conditional reliability ¨ Voting ¨ Repair ¨ Applying redundancy to software and data ¨ Lessons n Next time ¨ Atomicity (Chapter 9)
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5/13/10 Triple-redundant super-module with three voters 33 M 1 M 2 M 3 V 1 V 2 V 3
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5/13/10 Reliability increases for triple-modular redundancy when mission time is short compared with MTTF 44 0 .00025 .0005 .001 Mission time, in units of MTTF 1.0000 0.9997 0.9993 0.9990 0.9987 0.9983 0.999 one engine .999997 three engines .00075
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5/13/10 When mission time is comparable with MTTF reliability for the triple modular redundancy decreases 55 1.0 0.8 0.6 0.4 0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.25 single engine 0.15 three engines
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Unformatted text preview: previous figure Mission time, in units of MTTF 5/13/10 Effects of Replication n Replication provides a dramatic improvement for missions of short duration compared with the MTTF. n MTTFsystem=ln(MTTFreplica) 66 5/13/10 5 4 3 2 1 Number of still working replicas time 5MR with fail-fast replicas fails 5MR with purging fails 5MR with fail-vote fails correctly Failure points for a five-modular redundancy system 5/13/10 88 procedure CAREFUL _ GET ( data , sector_number ) for i from 1 to NTRIES do if FAIL _ FAST _ GET ( data , sector_number ) = OK then return OK return BAD procedure CAREFUL _ PUT ( data , sector_number ) for i from 1 to NTRIES do if FAIL _ FAST _ PUT ( data , sector_number ) = OK then return OK return BAD 5/13/10 99...
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Lecture15 - previous figure Mission time, in units of MTTF...

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