1. COP 5611 Operating Systems Spring 2010
Dan C. Marinescu
Office: HEC 439 B
Office hours: M-Wd 1:00-2:00 PM

2. Lecture 15 Reading Assignment: Chapter 9 from the online textbook
Homework 3 due today. Midterm: Wednesday March 17
Last time:
Coding
Replication
Voting
Today:
Conditional reliability
Repair
Applying redundancy to software and data
Lessons
Next time
Atomicity (Chapter 9) 2 2 2 2 2

3. Triple-redundant super-module with three voters

4. Reliability increases for triple-modular redundancy when mission time is short compared with MTTF

5. When mission time is comparable with MTTF reliability for the triple modular redundancy decreases

6. Effects of Replication
Replication provides a dramatic improvement for missions of short duration compared with the MTTF.
MTTFsystem=ln(MTTFreplica)

7. Failure points for a five-modular redundancy system