<P> For example, AFR is used to characterize the reliability of hard disk drives . </P> <P> The relationship between AFR and MTBF (in hours) is: </P> <Dl> <Dd> A F R = 1 − e x p (− 8766 / M T B F) (\ displaystyle AFR = 1 - exp (- 8766 / MTBF)) </Dd> </Dl> <Dd> A F R = 1 − e x p (− 8766 / M T B F) (\ displaystyle AFR = 1 - exp (- 8766 / MTBF)) </Dd>

What does annualized failure rate (afr) measure and what units are used