Annualized failure rate

Annualized failure rate
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Annualized_failure_rate".

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Annualized failure rate (AFR) is the relation between the mean time between failure (MTBF) and the assumed hours that a device is run per year, expressed in percent.

Example

A disk drive's MTBF number may be 1,200,000 hours and the disk drive may be running 24 hours a day, seven days a week¹. One year has 8,760 hours.

$\frac{1,200,000\,hours}{8760 \, hours / year}=136.9863 \, years$

then take the reciprocal of 136.9863 years

$\frac{1 \, failure}{136.9863 \, years}\times 100\%=0.73\%$

You can expect about 0.73 percent of the population of these disk drives to fail in the average year.

Another example: A disk drive's MTBF number may be 700,000 hours and the disk drive may be running 2400 hours a year².

$\frac{700,000 \, hours}{2400 \, hours / year}=291.6667 \, years$

then take the reciprocal of 291.6667 years

$\frac{1 \, failure}{291.6667 \, years}\times 100\%=0.34\%$

You can expect about 0.34 percent of the population of these disk drives to fail in the average year.

Now assuming you let the same disk run 24 hours a day, 7 days a week:

$\frac{700,000 \, hours}{8760 hours / year}=79.9087 \, years$

then take the reciprocal of 79.9087 years

$\frac{1 \, failure}{79.9087 \, years}\times 100\%=1.25\%$

You can expect about 1.25 percent of the population of these disk drives to fail in the average year.

References

^ Annualized Failure Rate (AFR) and Mean Time Between Failures (MTBF) in: Seagate Barracuda ES SATA Product Manual, Page 29, Chapter 2.12: Reliability
^ Annualized Failure Rate (AFR) and Mean Time Between Failures (MTBF) in: Seagate Barracuda 7200.10 SATA Product Manual, Page 42, Chapter 2.12: Reliability

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Example

See also

References