hesela.devAnnual sector error rate
Annual sector error rate (ASER) normalizes the mean count of latent sector errors per drive in a one-year window by the number of sectors per drive.
Denominator: ASER = E[X(t) - X(t - 12)] / S, with t in months and S sectors per drive; zero-error drives remain in the cohort mean [1].
A constructed example has 100 errors across 1,000 drives, each with 1,000,000 sectors for one year: ASER is 0.0000001 whether one drive or 100 drives contain those errors. The affected-drive fractions are instead 0.1% and 10% [3].
Do not convert capacity-normalized ASER to errors per bit read by multiplying the sector capacity by eight. Read exposure and error-counting conventions are different inputs. An ECC comparison, for example, defines UBER through codeword failure rate divided by codeword length [2].
Relations
- related
- Latent sector error, Uncorrectable bit error rate, Data scrubbing, Annualized failure rate (AFR)
Citations
- Bairavasundaram et al. An Analysis of Latent Sector Errors in Disk Drives. SIGMETRICS 2007, section 5.3.1 and Figure 2.
- Cai et al. Error Characterization, Mitigation, and Recovery in Flash Memory Based Solid-State Drives (2017), section VI.C.
- Hesela: ASER denominator examples with complete synthetic one-year cohorts.