On ensuring data recoverability by the use of error-correcting codes

The problem of controlling data errors in magnetic disc storage is one of fundamental importance. Data errors caused by electrical noise within the system are considered 'soft' and generally recoverable by retry of the data transfer operation, resulting in execution overhead. However, errors caused by inherent defects in the recording media or due to contamination are considered to be 'hard' and occur in 'bursts', in which case, consecutive bit positions are corrupted, as opposed to isolated 'random' errors. In the latter case, data is inevitably lost. This paper describes the effective use of error-correcting codes to combat burst errors in disc storage.