Data reliability on optical Data reliability on optical discsdiscs

Mladen TušekMladen TušekFilozofski fakultet, Ivana Lučića 3, ZagrebFilozofski fakultet, Ivana Lučića 3, Zagreb

Hrvatska Hrvatskamladentusek@yahoo.commladentusek@yahoo.com

IntroductionIntroduction

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

Long term data Long term data preservation on optical preservation on optical

discsdiscs• Physical damage• Chemical damage

-chemical layer “Phthalocyanine”

-reflexive gold layer

IdentificationIdentification of media of media

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

AnalysisAnalysis and and data recoverydata 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

ConclusionConclusion

• 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

• 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

Thank YouThank You