Browse Prior Art Database

Disk File Defect Strategy

IP.com Disclosure Number: IPCOM000061895D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Cunningham, EA: AUTHOR

Abstract

A typical method of compensation for defective sectors in a disk file is to provide extra sectors in each track as alternates for any sectors having defects making them unusable. This is effective when the number of defects is equal to or less than the number of extra sectors allotted. Where there are more defective sectors than the number of spares allotted on the track, a bad or defective track is defined. Extra tracks are allowed within a band of tracks, and, should the number of bad tracks exceed the number of allotted spares, the disk fails.

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Disk File Defect Strategy

A typical method of compensation for defective sectors in a disk file is to provide extra sectors in each track as alternates for any sectors having defects making them unusable. This is effective when the number of defects is equal to or less than the number of extra sectors allotted. Where there are more defective sectors than the number of spares allotted on the track, a bad or defective track is defined. Extra tracks are allowed within a band of tracks, and, should the number of bad tracks exceed the number of allotted spares, the disk fails.

The strategy proposed is to provide each band of tracks a number of spare sectors to be available as alternates for defective sectors. The sector numbering would be a complete "push-down" numbering system starting at the outside of the band (greater diameter) and numbering all good sectors sequentially, leaving all remaining good sectors at the inner diameter of the band where capabilities are normally poorest. A superior numbering system would classify more levels than just good and defective. If additional good sectors were available, the sectors may be selected. This would implement the use of some inner track sectors that may be superior to some marginally good sectors at other locations within the band. As in other strategies, if the number of defective sectors exceeds the extra sectors allotted, a bad disk is defined.

The proposed technique can tolerate more defects than the typical method...