Browse Prior Art Database

Use of Variable Track Pitch Allowed by Performance Variation

IP.com Disclosure Number: IPCOM000120542D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 76K

Publishing Venue

IBM

Related People

Cunningham, EA: AUTHOR [+2]

Abstract

Disclosed is a method of increasing the recorded capacity in a direct access storage device (DASD) by adjusting the recording pitch versus radius according to the differing radial capability on the average head/disk components.

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Use of Variable Track Pitch Allowed by Performance Variation

      Disclosed is a method of increasing the recorded capacity
in a direct access storage device (DASD) by adjusting the recording
pitch versus radius according to the differing radial capability on
the average head/disk components.

      Differences in the strength of magnetic recordings in DASD
often happen with constant frequency recording.  This is principally
a function of linear density versus radius, and flyheight versus
radius.  In one most commonly occurring case, a high linear density
at the inner radius will stress the recording system most, causing
the recording at the innermost rack to be easily damaged by
encroaching adjacent tracks, while tracks near the outer portion of
the disks, have much lower linear density, and have significantly
higher signal-to-noise ratio, allowing more interference of adjacent
tracks before there is a significant effect on the data reliability.
In this case, the pitch can be reduced for the outer tracks compared
to the pitch at the inner tracks, thus producing added capacity.  The
extra capability can also be used for increased performance or
reliability at the same capacity by using a smaller than nominal
pitch at the outer tracks, while allowing a larger pitch than nominal
at the inner tracks, therefore producing less stress on those tracks.
The allowed variation in pitch can be tested versus radius to
determine the occurrence of hard errors for extreme adjacent track
misregistration and head capability.

      A second, much less recognized case can occur when the
recording linear density is not very high, where there is not much
more stress in the recording at the inner t...