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AFR will increase towards and beyond the end of the service life of a device or component. Google's 2007 study found, based on a large field sample of drives, that actual AFRs for individual drives ranged from 1.7% for first year drives to over 8.6% for three-year-old drives. A CMU 2007 study showed
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for the full 8766 hours of a year, and gives the estimated fraction of an original sample of devices or components that will fail in one year, or, equivalently, 1 − AFR is the fraction of devices or components that will show no failures over a year. It is based on an exponential failure distribution
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drives may be an MTBF of 300,000 hours, giving an approximate theoretical 2.92% annualized failure rate i.e. a 2.92% chance that a given drive will fail during a year of use.
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The AFR for a drive is derived from time-to-fail data from a reliability-demonstration test (RDT).
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an estimated 3% mean AFR over 1–5 years based on replacement logs for a large sample of drives.
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Disk
Failures in the Real World: What Does an MTTF of 1,000,000 Hours Mean to You?
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Estimating Drive
Reliability in Desktop Computers and Consumer Electronics Systems
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for a full derivation). Note: Some manufacturers count a year as 8760 hours.
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statistics that can not predict the behaviour of an individual unit.
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Probability that a device or component will fail during a year of use
249:"Diving into "MTBF" and "AFR": Storage Reliability Specs Explained"
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255:. Seagate. Apr 2010. Archived from the original on 2010-05-01.
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For example, AFR is used to characterize the reliability of
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This ratio can be approximated by, assuming a small AFR,
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This equation assumes that the device or component is
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The relationship between AFR and MTBF (in hours) is:
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319:Failure Trends in Large Disk Drive Population
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282:Hard disk drive reliability and MTBF / AFR
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196:For example, a common specification for
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186:{\displaystyle AFR={8766 \over MTBF}}
118:{\displaystyle AFR=1-exp(-8766/MTBF)}
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316:"AFR broken down by age groups",
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226:Frequency of exceedance
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232:References
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261:cite web
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202:SATA
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