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Data Recovery Procedure for Magneto-Optical Recorded Pulse Width Modulation Data that has Suffered Edge Shift Data Degradation

IP.com Disclosure Number: IPCOM000116352D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Belser, K: AUTHOR [+3]

Abstract

It is known that domain edge motion occurs with Pulse Width Modulation (PWM) magneto-optical recording that is caused by a combination of high ambient disk temperature and read power. Edge motion starts to occur at typical read power levels making data that is read many times subject to data loss. This degradation decreases very rapidly with the lowering of the read power level so that essentially no edge motion occurs at half of the typical read power levels. The solution to this problem is as follows: 1. The drive must contain a thermal sensor or other means to insure that the media never exceeds a maximum temperature. 2. The drive must reduce the read power to prevent it from exceeding the no-edge-motion read power threshold except when reading.

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Data Recovery Procedure for Magneto-Optical Recorded Pulse Width
Modulation Data that has Suffered Edge Shift Data Degradation

      It is known that domain edge motion occurs with Pulse Width
Modulation (PWM) magneto-optical recording that is caused by a
combination of high ambient disk temperature and read power.  Edge
motion starts to occur at typical read power levels making data that
is read many times subject to data loss.  This degradation decreases
very rapidly with the lowering of the read power level so that
essentially no edge motion occurs at half of the typical read power
levels.  The solution to this problem is as follows:
  1. The drive must contain a thermal sensor or other means to insure
      that the media never exceeds a maximum temperature.
  2.  The drive must reduce the read power to prevent it from
exceeding
       the no-edge-motion read power threshold except when reading.
       Note that any data sector that gets read is always checked by
the
       Error Correction Code (ECC) so that any damage is immediately
       detected.
  3.  The drive must copy the ECC corrected data into a spare sector
       for any sector whose data has too many errors.  The data is
       securely written in a spare sector at this point and the
       secondary defect list is updated.  Note that if edge motion
       caused the errors, then the original sector may not be bad.
  4.  Erase, write and...