Specifying reliability in the disk drive industry: No more MTBF's

Great strides have been made in creating a more realistic method for specifying disk drive reliability in a competitive commercial environment. Mean time between (before) failure (MTBF) is misleading and causes great conflict between drive manufacturers and drive integrators. The single most prominent cause is that the failure distribution for disk drives is not exponential during the first year of product use. To rectify this problem, drive hazard rate, in the form of a stair-step approximation to the Weibull, has been instituted as a standard way of representing reliability in the disk drive industry. Although not problem free, this method for specifying reliability is more easily correlated to field experience and can be used to more accurately calculate the expected number of returns and spares needed.