Operating System - RAID The reliability of a hard-disk drive is typically descri

Question

Operating System - RAID

The reliability of a hard-disk drive is typically described in terms of a quantity called mean time between failures (MTBF). Although this quantity is called a “time,” the MTBF actually is measured in drive-hours per failure.

If a system contains 1,000,000 drives, each of which has a 100,000 hour MTBF, which of the following best describes how often a drive failure will occur in that disk farm: once per thousand years, once per century, once per decade, once per year, once per month, once per week, once per day, once per hour, once per minute, or once per second?

Explanation / Answer

drives = 1,000,000 drives
mean time between failures (MTBF) = 100,000 hour MTBF
100,000 drive-hours per failure divided by 1,000,000 drives gives 0.1 hours per failure
=>  about 6 minutes or once per 360 seconds.

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