Data reliability on optical discs Mladen Tu

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Data reliability on optical discs Mladen
TušekFilozofski fakultet, Ivana Lucica 3,
Zagreb Hrvatskamladentusek_at_yahoo.com
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Introduction

• Optical discs suitable for preserving data
• CD 650 or 700 MB
• DVD 4,7 or 9 GB
• HD DVD 15 or 30 GB
• Blu-Ray 25 or 50 GB

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Long term data preservation on optical discs

• Physical damage
• Chemical damage
• -chemical layer Phthalocyanine
• -reflexive gold layer

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Identification of media

• Identification of disc manufacturer
• Identification of chemical layer
• Other relevant information about optical disc

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Analysis and data recovery

• Disc reading speed as indication of data status
  on discs chemical layer
• Aging of chemical layer causing data loss on all
  optical discs of the same manufacturer
• Unequal quality of chemical layer causes data
  loss on one or more optical discs

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Conclusion

• Using quality discs, two of them with different
  chemical layer and manufacturer
• Parallel data writing on two computers with two
  different data recorders (different
  manufacturers Plextor and Pioneer, for example).
• Low speed recording (4x) and mandatory data
  verification after recording
• After data recording test readability of recorded
  disc in different optical devices

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• After one recording session and before erasing
  source data make readability test
• During archiving process in regular intervals
  (every 6 months) check readability using random
  method
• In case of problem use specialized applications
  and copy content of optical disc before
  irreversible data loss occur

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Thank You