Annualized failure rate

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Annualized failure rate

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 week [Annualized Failure Rate (AFR) and Mean Time Between Failures (MTBF) in: [http://www.seagate.com/staticfiles/support/disc/manuals/enterprise/Barracuda%20ES/SATA/100424667b.pdf Seagate Barracuda ES SATA Product Manual] , Page 29, Chapter 2.12: Reliability] . One year has 8,760 hours.

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

then take the reciprocal of 136.9863 years

:$frac\left\{1 , failure\right\}\left\{136.9863 , years\right\} imes 100%=0.73%$

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 year [Annualized Failure Rate (AFR) and Mean Time Between Failures (MTBF) in: [http://www.seagate.com/staticfiles/support/disc/manuals/desktop/Barracuda%207200.10/100402371f.pdf Seagate Barracuda 7200.10 SATA Product Manual] , Page 42, Chapter 2.12: Reliability] .

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

then take the reciprocal of 291.6667 years

:$frac\left\{1 , failure\right\}\left\{291.6667 , years\right\} imes 100%=0.34%$

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:

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

then take the reciprocal of 79.9087 years

:$frac\left\{1 , failure\right\}\left\{79.9087 , years\right\} imes 100%=1.25%$

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

ee also

* Failure rate

References

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