Patent ID: 8786972

Claim:
A magnetic recording disk drive comprising: a magnetic recording disk having a recording surface with a plurality of circular data tracks containing data sectors, the data sectors containing magnetizable data regions, each data region representing a data bit; a write head associated with said disk surface for writing desired data patterns in the sectors by generating a magnetic write field to magnetize the data regions; a read head for detecting the magnetic state of the data regions in the sectors; a detector coupled to the read head for detecting the magnetic state of the data regions into data patterns of data bits; an error corrector for correcting bit errors in the detected data patterns; a controller for synchronizing the reading and writing of data to individual data regions; and memory coupled to the controller and containing a program of instructions readable by the controller for recovering data written to data sectors containing defective data regions, the program of instructions undertaking the method acts comprising: (a) determining that a data pattern in a sector cannot be corrected by the error corrector; (b) storing in memory the uncorrectable data pattern; (c) writing a predetermined nondata pattern to the sector containing said uncorrectable data pattern; (d) reading said written predetermined nondata pattern; (e) identifying the location of defective data regions in said sector that cannot be corrected by comparing the read predetermined nondata pattern with the written predetermined nondata pattern; (f) attempting to correct, with the error corrector, said data pattern that cannot be corrected by marking bits representing the identified defective data regions as hard bit errors; and if at step (f) said data pattern can be corrected, writing the corrected data pattern to a different sector and then marking the sector for said data pattern as bad.