Browse Prior Art Database

Precursor for Head Disk Interface Failure

IP.com Disclosure Number: IPCOM000115860D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Horne, D: AUTHOR [+2]

Abstract

It has been shown in (*), that track-to-track comparison of a sample of the readback amplitude from a recording disk, provides a measure of the accumulated damage at the head-disk interface. This measurement provides a precursor which can be used to diagnose defective files. In the current publication we propose that damage can be detected at a lower threshold than that described above by making measurements of the readback amplitude at several locations round each track.

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Precursor for Head Disk Interface Failure

      It has been shown in (*), that track-to-track comparison of a
sample of the readback amplitude from a recording disk, provides a
measure of the accumulated damage at the head-disk interface.  This
measurement provides a precursor which can be used to diagnose
defective files.  In the current publication we propose that damage
can be detected at a lower threshold than that described above by
making measurements of the readback amplitude at several locations
round each track.

      Three algorithms are described for the derivation of
precursors.  For each the signals are normalized by dividing the
value of the readback amplitude observed at time t, by the value
observed at that location initially.  The ratio will be close to one
for all locations on an undisturbed disk.

      The first algorithm is to calculate the mean ratio for each
track.  This is a more sensitive estimator of the track damage than
the single sample described in the patent referred to above.  It
normalizes the circumferential variation of the disk and it samples
more efficiently than the estimator described in the previous patent.
The second algorithm is to calculate the minimum and maximum values
of the ratios on each track.  The precursor consisting of the track
to track variation of this set of maxima and minima is more sensitive
to head disk interactions than the comparison of track mean values.
It allows recognition of damage which s...