Research unit studying data storage on digital optical disks

Questions concerning the reliability of digital optical disks for data archiving
A research unit to study digital optical disks
The six partners
Scientific steering committee
Permanent contributors
Research programme
Initial results
Contacts

Latest update: July 2010

Questions concerning the reliability of digital optical disks for data archiving

Digital optical disks

Human activities generate an ever-increasing amount of data of all kinds, including text, audio and visual documents. This constant daily output is further expanded by the retro-digitization programmes carried out all over the world so that old documents may be consulted and indexed more easily. E-archiving involves a major ongoing investment to preserve a precious heritage for future generations.

However, we are faced with a problem of alarming proportions. Digital technology is highly convenient for storing very large quantities of data, but this data is stored on physical and chemical surfaces whose life is relatively short, since they have not been designed to last indefinitely. If data archives are not regularly recopied, there is a real risk that information will be lost for ever after only a few years. The situation is all the more serious since there seems to be a general taboo surrounding this problem, meaning it is rarely discussed. For example, the general public is largely unaware that the digital data kept by hospitals (imaging, etc.) is by no means safe.

Recent studies showed that certain brands of magnetic media (hard disks and tapes) and optical disks (CD-Rs and DVD-Rs) were unusable after a storage period of around one year, while other brands showed no notable deterioration after 15 years of archiving.

A research unit to study digital optical disks

In 2004 a digital optical disk research unit (GIS-DON) was formed to study these questions, on the initiative of LNE. Set up as a Scientific Interest Group (Groupement d'Interêt Scientifique, GIS), it brings together six research bodies specializing in the field. The research unit's objectives are to improve the conservation of data recorded on digital optical disks, identify stable e-archiving solutions and advise all parties concerned in their choice of media and optimum conditions of use. Heritage bodies, government departments, manufacturers of digital optical disks and users will thus all be able to contribute more effectively to ensuring the long-term conservation of valuable archives.

The research unit's member bodies also cooperate closely with standardization committees (ISO, AFNOR, AES), informing them of the results of the studies they carry out and thus contributing to the development of standards in this field.

The six partners

- The Musical Instrument and Acoustics unit of the Jean Le Rond d'Alembert Institute (LAM), a research unit run by the National Scientific Research Centre (CNRS), Pierre et Marie Curie University (Paris VI) and the French Ministry of Culture and Communication. The LAM specializes in signal analysis and ageing of sound archives.
- The Information Technology Electronics Laboratory of the French Atomic Energy Commission (CEA-LETI). It specializes in the design of new types of optical disks and is working on disks capable of storing 100 GB over 100 years.
- The Laboratory of Molecular and Macromolecular Photochemistry (LPMM), run by the CNRS and Blaise Pascal University, Clermont-Ferrand. The LPMM specializes in the chemical ageing processes of organic materials.
- The National Metrology and Testing Laboratory (LNE), whose areas of expertise include assessment of the hardware and software used to save data and conservation of recorded media.
- The National Audiovisual Institute - Inathèque de France (INA), whose mission is to preserve and digitize all audiovisual archives in danger of deterioration and destruction over time.
- The Material to System Integration Laboratory (IMS), a research unit of the University of Bordeaux 1, which specializes in failure analysis and determining the wear mechanisms of micro and nano-assembled devices.

Scientific steering committee

The digital disk research unit is steered by a scientific committee comprising eleven key figures from the ministries concerned and research laboratories. They decide on the unit's strategy and programme and the work to be undertaken, in consultation with the Research and Technology department of the Ministry of Culture and Communication (particularly for heritage aspects).

[Members of scientific committee] (235 kB)

Permanent contributors

Several parties with specific experience of the data archiving problem and/or particular needs in this field are invited to participate in meetings of the research unit's steering committee.

[List of permanent contributors] (191 kB)

Research programme

The research programme covers three objectives:

- improving our knowledge of the physico-chemical phenomena affecting the ageing of optical disks
- improving the characterization of disks on which data has been recorded
- studying new technological processes that could guarantee the integrity and perenniality of data stored on optical disks.

The studies carried out in the context of this programme aim to solve some of the problems concerning archiving, particularly for CD-R and DVD±R optical disks.

These studies will be extended through assistance to institutions responsible for heritage archiving. This will include assessment of industry services, such as the work carried out by the Optical Storage Technology Association (OSTA). The assistance provided will cover the following points in particular:

- the initial choice of disks to be used for archiving
- qualification of the data writing chain
- assessment of existing archives.

Initial results

Five studies have been completed since the digital disk research unit was set up. They have focused on the condition of data collections recorded on CD-R, the quality of recordable optical disks, and the suitability of these disks for long-term archiving.

DVD optical disk research programme (collective study carried out for the Ministry of Culture and Communication, 2004)

CD ageing study

Examination of the CD-R collection of the National Broadcasting Archives (INA) for radio copyright registration (study carried out for the Department for Business and Enterprise, 2006): In 2006, at the request of the Department for Business and Enterprise, LNE completed a study of the state of preservation of the INA's collection of radio programmes broadcast since 1994, recorded on some 180,000 CD-Rs. The study revealed a considerable difference in quality between the earliest and most recent CD-Rs. LNE therefore recommended setting up a procedure for creating and monitoring archives on optical disks (in the context of copyright registration of radio programmes) and a similar procedure for archiving television programmes on DVD±Rs.

Quality of digital optical disks conserved in public archives (study carried out for France's National Archives Office, 2005): In 2005 the National Archives Office asked LNE to assess the condition of the CD-R collections held by public archives departments. The study reviewed different CD-R archiving practices and revealed considerable variations in quality according to the department, the types of disk used and the disk writing hardware/software.

Quality and archiving suitability of DVD±R/RWs (study carried out for the National Consumer Organization, 2006): In partnership with the National Consumer Organization (INC), LNE assessed the quality and suitability for data archiving of 20 brands of DVD±R/RW. The study revealed wide variations in performance between brands and according to the type of recordable layer (coloring for DVD±Rs and phase-change for DVD±RWs). The full results of the study were published in the INC magazine 60 Millions de Consommateurs (no. 410, November 2006).

Quality of recordable optical disks for digital data archiving (study carried out for the National Archives Office, 2006): LNE was asked by the National Archives Office to identify the best combinations of disk writer and CD-R for archiving purposes. Eleven writers were tested with seven brands of disk. The study was carried out in three stages:
- selecting the writers that performed best with each brand of CD-R
- determining the optimum recording speed
- determining whether the recorded data could be read satisfactorily after accelerated ageing.
Each archive department was informed of the writer-disk combinations recommended by LNE. The results were also published on the LNE website.