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Browse Prior Art Database

New Method for Skipping Defects on a DASD Disk

IP.com Disclosure Number: IPCOM000105219D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 46K

Publishing Venue

IBM

Related People

Burton, PT: AUTHOR [+3]

Abstract

Disclosed is a method for skipping defective track cells in a direct access storage device (DASD). In the prior art, the control unit (CU) would perform a calculation in the gap preceding a field of cells to determine whether any of the cells were defective. The new implementation frees the CU from this function by shifting the responsibility to the device adapter (DA).

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This is the abbreviated version, containing approximately 70% of the total text.

New Method for Skipping Defects on a DASD Disk

      Disclosed is a method for skipping defective track cells in a
direct access storage device (DASD).  In the prior art, the control
unit (CU) would perform a calculation in the gap preceding a field of
cells to determine whether any of the cells were defective.  The new
implementation frees the CU from this function by shifting the
responsibility to the device adapter (DA).

      In the manufacture of a DASD device, the surface of the disk is
analyzed, and any defective cells are recorded in a list.  This list,
in turn, is written to the home address (HA) and each count field of
a track.

      The DA reads and retains the defect list from the count field.
It then identifies defective cells by examining each cell, one at a
time, during the data transfer rather than doing a calculation ahead
of the field.

      When the DA processes a count field, it retains the cell number
of each defective cell in its order of occurrence on the track.  A
pointer to the defect list is incremented after each occurrence of a
defect.  The DA also keeps track of the next occurring cell number.

      Before each cell, the DA compares the next occurring cell
number to the defective cell number at the current pointer.  If a
match occurs, current data transfer operations are suspended until
the defect has been skipped.  The pointer is then incremented to the
next defective cell number.  When all defective cells have b...