Availability
Topic appears in the following WE1 Exams:
- 2021 07 26 Q2 (5 points)
- 2021 02 05 Q3 (3 points)
Therefore it appears in 33% of the WE1 exams and it is worth 4 points on average.
Summary
- Mean Time to Repair (MTTR): Average time between the occurrence of a fault and service recovery, also known as the downtime
- Mean Time To Failures (MTTF): Mean time between the recovery from one incident and the occurrence of the next incident, also known as uptime
- Mean Time Between failure (MTBF): Mean time between the occurrences of two consecutive incidents
We can then define:
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Availability: The probability that a component is working properly at time t $$A = MTTF / (MTTF+MTTR)$$
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Reliability: The probability that a component has always been working properly during a time interval (0,t) R = e-λt λ = 1/MTTF