The present disclosure relates to a system for detecting a plurality of defect
types on the surface of a disk in a hard disk drive. In particular, the disclosure
relates to utilizing information obtained from a plurality of servo bits to determine
if a sector contains a physical defect. Where such a defect is found, the sector's
write gate is disabled and its burst signal data is ignored for track following
purposes. In addition, large changes in PES are used to identify closure spike
defects. Such defects are managed by providing a compensation signal to the read
value of the PES to improve track following. Finally, high PES values are used
to signal a third defect type where no other signs of defect are present. In such
case, the sector is mapped as defective, but the burst signals continue to be used
for track following purposes.
