Browse Prior Art Database

Self Correcting DASD

IP.com Disclosure Number: IPCOM000048678D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Starbuck, RE: AUTHOR

Abstract

U.S. Patent 3,997.876 describes an arrangement for avoiding defects which are located on concentric tracks of a magnetic disk file. In the disclosed arrangement of the patent, the format of each track is a conventional count-key-and-data format in which the track is initialized at the factory with Home Address and Record 0 fields. A portion of the Home Address and Record 0 fields are reserved for recording a "skip displacement" value which indicates to the storage system the location of the defect. In some commercial disk file arrangements, more than one skip displacement field is provided, allowing multiple defects to be bypassed on the same track. The surface defect detection and initial track formatting of the disk is done at the factory during a surface analysis routine.

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Self Correcting DASD

U.S. Patent 3,997.876 describes an arrangement for avoiding defects which are located on concentric tracks of a magnetic disk file. In the disclosed arrangement of the patent, the format of each track is a conventional count-key-and-data format in which the track is initialized at the factory with Home Address and Record 0 fields. A portion of the Home Address and Record 0 fields are reserved for recording a "skip displacement" value which indicates to the storage system the location of the defect. In some commercial disk file arrangements, more than one skip displacement field is provided, allowing multiple defects to be bypassed on the same track. The surface defect detection and initial track formatting of the disk is done at the factory during a surface analysis routine.

The present method is directed to locating a correctable data check that occurs a certain number of times at the same address on a track and altering the skip displacement values for the track, causing the newly located defect to be bypassed when the address is accessed in the future.

The method involves the direct-access storage device (DASD) keeping a dynamic record of all correctable data checks as they occur during normal usage. When a given threshold of correctable errors is exceeded for a single track, a micro program in the device controller transfers all the data on the offending track to a spare track. The program then reformats the track by rewriting the skip di...