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Distinguishing Between Media Flaws and Contamination in Optical Drives

IP.com Disclosure Number: IPCOM000115540D
Original Publication Date: 1995-May-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 6 page(s) / 252K

Publishing Venue

IBM

Related People

Klodnicki, EJ: AUTHOR

Abstract

Because recoverable read or write errors happen as a part of normal optical disk operations, it is difficult to distinguish the recoverable errors that are caused by manufactured flaws in the media, from the errors that are caused by contaminants inside of the optical drive.

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This is the abbreviated version, containing approximately 36% of the total text.

Distinguishing Between Media Flaws and Contamination in Optical Drives

      Because recoverable read or write errors happen as a part of
normal optical disk operations, it is difficult to distinguish the
recoverable errors that are caused by manufactured flaws in the
media, from the errors that are caused by contaminants inside of the
optical drive.

      It is desirable to distinguish the errors caused by media flaws
from those caused by contaminants.  Excessive contamination can lead
to non-recoverable errors and possible loss of information.  If it is
known that an optical drive is experiencing errors due to
contaminants inside of the optical drive, steps can be taken to clean
the optical drive before non-recoverable errors occur.  Cleaning the
drive after every recoverable read or write error is not appropriate
because media flaws can account for hundreds of recoverable errors on
a media surface.  If a user cleans the optical drive whenever a
recoverable drive error occurs, a media flaw would have the user
constantly cleaning the optical drive.  The result will be that the
user will stop cleaning the drive because cleaning is not working and
the user will either unnecessarily call for service or will learn to
ignore recoverable errors.  If the optical drive becomes
contaminated, the user will ignore the recoverable errors once again
and probably encounter a non-recoverable error and a possible loss of
information.

      If the errors caused by media defects can be separated from
those caused by contaminants, a better judgement can be made in
determining the appropriate time to clean the optical drive.

      When an optical drive encounters a problem during a read or
write operation, it recovers from the problem by rewriting the
information in a spare sector.  The optical drive then specifies the
track and sector number of the problem sector in the sense
information which is returned in its response to the read or write
command.  If the track and sector numbers and volume names for some
number of errors is saved as a history in an error log, the
information can be analyzed as described below to determine if a
media flaw exists.  If none of the errors in the history information
can be attributed to a media flaw, the errors can be assumed to be
caused by contaminants.

      This article discusses techniques for distinguishing between
errors caused by manufactured media flaws and errors caused by
contamination, for the following types of optical media:
  o  Media that is manufactured with an integer number of sectors per
      revolution and an integer number of tracks per revolution (for
      example, 17 sectors per revolution)
  o  Media that is manufactured with bands of tracks where there is
an
      integer number of sectors per track but not an integer number
of
      sectors per revolution (for example, 20.15 sectors per
revolution)

      Technique for Media with Integer...