Annualized failure rate
Encyclopedia
Annualized failure rate is the relation between the mean time between failure (MTBF
) and the hours that a number of devices are run per year, expressed in percent. AFR does not specifically apply to a single component, but rather to a population of like components. AFR and MTBF as given by vendors may be population
statistics that are not relevant to individual units.
drives may be 300,000 MTBF, implying that in a 600,000 drive sample, one drive failure may occur per hour if failures were evenly distributed, translating to 8760 drive failures per year or a theoretical 1.46% annualized failure rate.
Seagate
estimates the MTBF for a drive as the number of power-on hours per year divided by the first year AFR. The AFR for a drive is derived from time-to-fail data from a reliability-demonstration test (RDT).
Google's 2007 study found that actual AFRs for individual drives ranged from 1.7% for first year drives to over 8.6% for three-year old drives.
Failure rate
Failure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. It is often denoted by the Greek letter λ and is important in reliability engineering....
) and the hours that a number of devices are run per year, expressed in percent. AFR does not specifically apply to a single component, but rather to a population of like components. AFR and MTBF as given by vendors may be population
Statistical population
A statistical population is a set of entities concerning which statistical inferences are to be drawn, often based on a random sample taken from the population. For example, if we were interested in generalizations about crows, then we would describe the set of crows that is of interest...
statistics that are not relevant to individual units.
Hard drives
A vendor-quoted MTBF implies that half the drives in a large population will fail within that time of operation. For example, a common specification for PATA and SATASata
Sata is a traditional dish from the Malaysian state of Terengganu, consisting of spiced fish meat wrapped in banana leaves and cooked on a grill.It is a type of Malaysian fish cake, or otak-otak...
drives may be 300,000 MTBF, implying that in a 600,000 drive sample, one drive failure may occur per hour if failures were evenly distributed, translating to 8760 drive failures per year or a theoretical 1.46% annualized failure rate.
Seagate
Seagate Technology
Seagate Technology is one of the world's largest manufacturers of hard disk drives. Incorporated in 1978 as Shugart Technology, Seagate is currently incorporated in Dublin, Ireland and has its principal executive offices in Scotts Valley, California, United States.-1970s:On November 1, 1979...
estimates the MTBF for a drive as the number of power-on hours per year divided by the first year AFR. The AFR for a drive is derived from time-to-fail data from a reliability-demonstration test (RDT).
Google's 2007 study found that actual AFRs for individual drives ranged from 1.7% for first year drives to over 8.6% for three-year old drives.