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Browse Prior Art Database

Zone or Band-Based DASD Error Compensation Mechanism

IP.com Disclosure Number: IPCOM000115613D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Ouchi, NK: AUTHOR

Abstract

Disclosed is a mechanism where the error compensation design is matched to the error characteristics of zones or bands of tracks so that a constant net error rate is achieved. This provides a net savings in capacity compared to uniform use of the error compensation mechanism for the worse case zone. This mechanism can be used in combination with zone recording to achieve constant bit density and net error rate.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Zone or Band-Based DASD Error Compensation Mechanism

      Disclosed is a mechanism where the error compensation design is
matched to the error characteristics of zones or bands of tracks so
that a constant net error rate is achieved.  This provides a net
savings in capacity compared to uniform use of the error compensation
mechanism for the worse case zone.  This mechanism can be used in
combination with zone recording to achieve constant bit density and
net error rate.

      DASD disks have defects that may cause errors in the reading of
data written on the disk.  Mechanisms to compensate for these defects
include the addition of error correction codes or the skipping over
areas with defects using sector sparing or defect skipping.  Each of
these mechanisms reduces the net usable capacity of the disk.  The
error compensation mechanism is applied consistently across the
entire surface of the disk.  However, the error characteristics are
not consistent across the disk.  Major factors that contribute are:
bit density is higher at the inner radius compared to the outer
radius, the head flies higher at the outer radius, the disk finish
and coating process varies by radius, etc.  Most of the major error
sources correlate to the radius of the track.

      The disk surface is divided into zones or bands of equivalent
raw error rate and an error compensation mechanism is developed for
each zone.  Each error compensation mechanism can have error
correction codes and allocation of track capacity for defect s...