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Oct 10, 2024 · Paper, Microfilm/Microfiche, and Optical Media. Magnetic Media and Solid State media are only viable as “short term” backup or storage as they are too fragile.
Optical storage refers to a class of data storage systems that use light to read or write data to an underlying optical media. Although a number of optical formats have been used over time, the most common examples are optical disks like the compact disc (CD) and DVD.
- Introduction
- Logical Structure
- Iso9660
- Joliet/Hfs
- UDF
- CD-DA
- Applications in Preservation Workflows
- Future Research
- Appendix
- Correction
The role of optical media in archives has shifted in the past decade from preservation medium to at-risk format. While longevity models estimated a lifespan of 25-200 years for recordable media, recent testing has found this range to be optimistic by orders of magnitude. One collection of data CD-Rs from the 1990s yielded a 92% failure rate after a...
It is crucial to understand the logical layout of optical media before attempting any preservation activities. As the first optical media standard was IEC 60908 (1982) for audio storage and playback, future standards reflected a media-centric approach in how they structure the disc. Thus, despite standards such as ISO/IEC 10149 (available as ECMA-1...
ISO9660 is the most common format for carrying data on CD-ROMs, often appearing as the baseline filesystem on cross-platform discs. It is also common for it to serve as the foundational filesystem for more sophisticated systems, such as Joliet and HFS – these often (but not always) serve as a layer on top of ISO9660 data to provide additional funct...
While ISO9660 is the most common data format for CD-ROM, it is rarely seen by itself. Due to the restrictions on file structures, there was a demand for some mechanism to expand the capabilities for CD-ROM filesystems. To address this, Microsoft established the Joliet specification as an extension to ISO9660 in 1995. Joliet’s primary improvements o...
Since UDF was designed as a universal standard for data storage, it has few surprises for preservation. As opposed to a compact disc, a DVD will almost certainly (barring unusual circumstances) behave in a standard fashion across any number of devices. Despite the apparent variations between DVD-Video, DVD-Audio, and data DVDs, the underlying disc ...
The data structure of a CD-DA is more akin to tape than a traditional data disk. Instead of dividing the storage area into discrete files, CD-DA data is written as a linear pulse-code modulation (PCM) stream, divided into separate tracks. As the data is read by the disc drive (at 44,100 16-bit samples per second, chosen specifically to be above the...
The most important analysis an archivist can perform on a disc occurs before it ever enters a workstation. Recordable optical discs are frequently used by individuals as simple portable file carriers – for example, a donor may burn a DVD with material to transport as part of their collection, or a disc may be created to share documents around an of...
The current state of preservation research with regard to optical media is rather lacking, as it limits its scope to the physical artifact. While relevant in the short term, the inevitability of disc rot, coupled with the decrease in the manufacture of quality drives, places an urgent imperative on migration research and practice. As there has been...
CD-ROM Suggested Workflow
1. Analyze disc with ISOBuster and determine workflow (with a particular focus on CD-DA, number of tracks/sessions, and initial errors) 2. If the disc is CD-ROM only, analyze for structure (ISO-based, HFS, hybrid, etc) and describe as per metadata standard 3. Extract CD -> User Data, or if non-data bytes are necessary (for byte-level alignment), RAW This will capture all CD-ROM sessions/tracks on a disc in a binary image. If User Data was selected, this can be mounted as a disc within...
CD-DA Suggested Workflow
Due to the complexity – and necessity – of properly configuring Exact Audio Copy (EAC), it is beyond the scope of a general document. A guide to the varying software and drive options can be found at the Hydrogen Audio Knowledge Base. Note that, while EAC’s software options can be generalized for preservation, every drive is unique and thus requires individual configuration. It is also prudent to align one’s drive with the AccurateRip database in order to compare individual drive accuracy...
Glossary
CD: Compact Disc. A format designed to hold audio data (and later expanded to general data) on a 12cm plastic disc, using a laser to read a series of pits and lands as binary data. CD-DA: Compact Disc – Digital Audio. The standard used to define the logical, physical, and data structures of audio discs. CD-R: Compact Disc – Recordable. A WORM (write once – read many) format allowing for compact discs to be created using consumer hardware. CD-ROM: Compact Disc – Read Only Memory. The standard...
When this article was first published, a citation to Figure 2 was missing and has since been added. We apologize for this oversight.
- Alexander Duryee
- 2014
Most of today's optical disks are available in three formats: compact disks (CDs), digital versatile disks (DVDs) -- also referred to as digital video disks -- and Blu-ray disks, which provide the highest capacities and data transfer rates of the three.
Nov 30, 2010 · Present optical data storage devices such as the compact disk (CD), the digital video disk (DVD), and the Blu-ray disk (BD), which are quite essential as audio and visual storage media and very popular, involve one-photon processes to write and retrieve data or information on a two-dimensional (2D) surface, and have nearly achieved an upper ...
- Yang Wang, Yiqun Wu, Haifeng Wang, Mingju Huang, Yan Wang
- 2011
Optical mass storage devices and systems can provide absolute data authenticity for a wide variety of markets and applications, including medical, financial, govern- ment, broadcast, and entertainment.
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• Teach the differences between CD, DVD, and Blu-ray disc (BD) optical storage systems, including how each new generation has been able to store more digital content. • Provide a quick overview of how data is organized on an optical disc. • Review a history of optical disc form factors.
