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…
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:
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Correct answer: (D) 99.97%
Explanation
Converting 30 days into minutes, the fraction of time the system is not available = 10/(30 × 24 × 60) × 100 ≈ 0.023%. Availability = 100 – 0.023 ≈ 99.97%.