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Soft-Sectored Hard File Defective Sector Mapping

IP.com Disclosure Number: IPCOM000042159D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Arroyo, RX: AUTHOR [+4]

Abstract

The maintenance of a Defective Sector Map is used to handle media defects on a magnetic disk. For each media defect, the map contains two pieces of information: (1) the address of the defective sector, and (2) the address of where the sector was relocated. To conserve space and increase simplicity, the map is position-dependent which allows the map to contain only one address for each media defect. To help performance, a subset of the Defective Sector Map, the Cylinder Defect Map, is created to speed defective sector searching. In addition, by handling media defects on a sector basis instead of a track basis, it allows for more efficient media usage. For soft-sectored hard files, which cannot rewrite the ID fields without formatting the entire file, this solution is advantageous.

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Soft-Sectored Hard File Defective Sector Mapping

The maintenance of a Defective Sector Map is used to handle media defects on a magnetic disk. For each media defect, the map contains two pieces of information: (1) the address of the defective sector, and (2) the address of where the sector was relocated. To conserve space and increase simplicity, the map is position-dependent which allows the map to contain only one address for each media defect. To help performance, a subset of the Defective Sector Map, the Cylinder Defect Map, is created to speed defective sector searching. In addition, by handling media defects on a sector basis instead of a track basis, it allows for more efficient media usage. For soft-sectored hard files, which cannot rewrite the ID fields without formatting the entire file, this solution is advantageous. One cylinder of the hard file is reserved to provide storage for the relocation of defective sectors and to contain the Defective Sector Map. The position- dependent map means that the first media defect discovered is always relocated to sector X on the reserved cylinder. The address of the defective sector is placed in the map as the first entry. The second entry in the map will always be relocated to sector X+1 on the reserved cylinder, and so on. To improve performance, a subset of the Defective Sector Map is created which contains all of the defective sectors on the cylinder that the R/W heads are currently over. This subset map, the Cylinder Defect Map, contains the same number of bytes as there are sectors on a cylinder, with each byte corresponding to a specific sector on the cylinder. After the steps have been issued for a seek...