data reliability on optical discs mladen tušek filozofski fakultet, ivana lučića 3, zagreb...

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