An Operating System (OS) crashes on the average once in 30 days, that is, the…
2016
An Operating System (OS) crashes on the average once in 30 days, that is, the Mean Time Between Failures (MTBF) = 30 days. When this happens, it takes 10 minutes to recover the OS, that is, the Mean Time To Repair (MTTR) = 10 minutes. The availability of the OS with these reliability figures is approximately :
- A.
96.97%
- B.
97.97%
- C.
99.009%
- D.
99.97%
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Correct answer: D
Answer: 99.97% (approximately)
Reason: Availability is given by MTBF / (MTBF + MTTR). Use consistent units when applying the formula.
Convert MTBF to minutes: 30 days × 24 hours/day × 60 minutes/hour = 43,200 minutes.
MTTR is already in minutes: 10 minutes.
Availability = 43,200 / (43,200 + 10) = 43,200 / 43,210 ≈ 0.999767 ≈ 99.9767%.
Rounded to two decimal places, the availability ≈ 99.97%.
Therefore the availability of the OS is approximately 99.97%.
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