Analysis of asymmetric deterministic bitshift errors in a hard disk file

An extensive statistical analysis of soft errors occurring in an IBM 3380 K hard-disk file has been made. About 90% of the errors was bitshift-induced involving a single bit. There was a high degree of early/late asymmetry. It is shown that decreasing system signal-to-noise ratio (S/N) increases the error rate, but reduces the early/late asymmetry. The repeatability of errors suggests that most errors happen at or near a media-direct site. Self-consistent write-process modeling, taking into account media defects, indicates bitshift and amplitude degradation commensurate with the experimental results