The GIS-DON was renamed GIS-SPADON when its constitutive agreement was renewed at the beginning of October 2012. It has thus become the Scientific Interest Group (Groupement d'Interêt Scientifique, GIS) on long-lasting media (Supports Pérennes, SP) for digital optical discs (DON) data Archiving.
The name change was decided in order to adapt to fast-evolving technologies and broaden the GIS interest scope to any digital information medium that can store information for several decades or even centuries.
Human activities generate an ever-increasing amount of digital data of all kinds, including text, audio and visual documents. This profuse daily production is further increased by the retro-digitization programs carried out all over the world, so that old documents may be consulted and indexed more easily. Digital archiving involves a major ongoing investment to preserve a precious heritage for future generations.
However, we are facing a very alarming statement: digital technology is highly convenient for storing very large quantities of data, but the physical media have a relatively short lifespan, since they have not been designed to last indefinitely. If data are not regularly copied, 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 and that, as a consequence, is rarely discussed. For example, people are largely unaware that the digital data kept by hospitals (imaging, etc.) are by no means safe.
Recent studies showed that certain brands of magnetic media (hard disks and tapes) and optical discs (CD-Rs and DVD-Rs) are unusable after a storage period of only one year, while other brands showed no notable deterioration after 15 years of archiving.
The GIS-DON was created in 2004 on the initiative of LNE. Set up as a Scientific Interest Group (“Groupement d'Interêt Scientifique”, GIS), it brings together six research bodies specialized in the field. The research objectives are to improve the conservation of data recorded on digital optical discs, identify stable archiving solutions and advise the concerned bodies (heritage institutions, manufacturers, users) in their choice of media and optimum conditions of use. Heritage bodies, government departments, manufacturers and users of digital optical discs will thus all be able to contribute more effectively to the heritage preservation.
The GIS-DON'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 GIS-DON is steered by a scientific committee composed of eleven key figures from the concerned ministries and research laboratories. They decide on the strategy and the program, in consultation with the Research and Technology department of the Ministry of Culture and Communication (particularly regarding heritage aspects).
[Members of scientific committee] (in french - 235 kB)
Parties with specific experience on data archiving and/or particular needs in this field are invited to participate inthe steering committee meetings.
[List of permanent contributors] (in french - 191 kB)
The research program covers three objectives:
The studies carried out in the context of this program aim to solve some of the problems regarding archiving, particularly for CD-R and DVD±R optical discs.
These studies will be extended through assistance to institutions responsible for heritage archiving. This will include assessment of optical disc models, such as the work carried out by the Optical Storage Technology Association (OSTA). The assistance provided will especially cover the following points:
The recording quality of CD-R depends on the recording speed and the adjustment of the drive to the disc model. Conservation of digital information over long periods depends also of the physical and chemical stability of the disc, particularly the recordable layer.
Synthesis of the study carried out in 2005 on the data preservation on CD-R (in french - 961 kB)
In 2006, 2008 and 2012 the Archives of France asked LNE to assess the ability for archiving of the models of recordable optical discs that are available in the market. This evaluation is mainly based on the comparison of the discs lifespan in harsh climatic conditions: 80 ° C with a relative humidity of 80-85%. These conditions accelerate the ageing processes and reduce sensibly the testing time. Some models of optical discs can store digital information in these severe conditions, for a duration of at least 2000 hours, while other models cannot withstand exposure to 250 hours.
List of recommended models (30 kB)
Recommended choices are the subject of a circular addressed to the regional archive services. They are also available on the website of the Archives of France.
Models of CD-R for archiving (Study report 2008 - 1 mB)
Models of DVD-R for archiving (Study report 2012 - 1,8 mB)
Models of BD-R for archiving (Study report 2012 - 1,5 mB)
In 2006, a study was conducted to evaluate the quality of the INA collection of 180 000 CD-R, which contains recordings of radio broadcasts since 1994. Analyzes were carried out on a sample of 1500 discs recorded between 1994 and 2004. The results show that the quality of the collection is generally good. The defects identified by the analysis are not due to natural ageing. In particular, a majority of the CD-Rs recorded in the early years keep a good quality, after ten years of storage.
LNE has made a collection of 68 CD-R recorded between 2000 and 2002. This collection includes 60 different models of that time. Analysis of the discs were made just after recording, then in 2004 and 2009. Half discs show no significant changes in 2009, but nearly a quarter are strongly or very strongly degraded.
Natural degradation of a collection of CD-R recorded between 2000 and 2002 (Study report 2009 - 3,9 mB)
A collection of 98 CD-R made by a private owner between 1994 and 2004 was analyzed in 2009. There is a great disparity between the 34 CD-R models in this collection. All the discs were undamaged for almost 40% of the models. In contrast, 40% of the models show some damaged discs and 18% of the models show only damaged discs. Observed degradations seem mostly due to ageing phenomena, which most often does not affect uniformly the surface of the disc.
State of a collection of 98 CD-R recorded between 1994 and 2004 (Study report 2009 - 3,1 mB)
A collection of 113 DVD±R recorded between 2004 and 2008 was analyzed in 2009 and then in 2011. This collection includes 60 different models. 7 models show significant ageing, sometimes with loss of data. The detailed analysis of the degraded discs shows a similarity with damages observed on CD-R. However, the distribution of the degraded areas on the DVD±R surface is more homogeneous, with fewer edge effects, than in the case of CD-R.
Natural degradation of a collection of DVD±R recorded between 2004 and 2008 (Study report 2011 - 0,7 mB)
In order to study ageing phenomena, the optical discs are put in harsh climatic conditions, more severe than those in usual preserving. The discs are placed in an oven at a temperature of 80°C with a high relative humidity level (85% for example). Under these conditions, chemical reactions and physical phenomena at the origin of the degradation of the discs are accelerated.
A study was conducted on two models of CD-R, with a fairly rapid evolution in harsh climatic conditions. In both cases, the degradation is greater at the outer edge of the discs than in their central part. However, the surface images of the error rate and the analysis of the HF signal show different behaviours. For one of the two models, the error rates are strongly correlated with the image printed on the back of the discs.
Ageing in harsh climatic conditions of 2 CD-R references (Study report 2007 - 1,9 mB)
A synthesis of the results of many tests and studies is made in order to describe a typology of the defects due to natural or accelerated ageing of CD-R. Different kinds of defect are shown, including in particular the emergence of micro-spots in the recording layer. The size of these spots does not exceed much the width of one or two grooves (2 to 3 µm). They often appear from the outer edge of the disc.
Typology of CD-R ageing (Study report 2010 - 9 mB)
The report "Longevity of Digital Information" of the Academy of Sciences and the Academy of Technologies recommends to explore new technology solutions dedicated to the preservation of digital data over the long term.
In this context, the Scientific committee of GIS-DON has wished to study the durability of two models of digital recordable optical disc made of glass. The two models have the DVD format.
First, the durability is compared to that of pressed DVDs, and second, to that of DVD±Rs whose recording layer is either organic or inorganic (M Disc, DataTresorDisc). The results obtained for the two models made of glass show the superiority of this technology for long-term archiving of digital data.
Durability of DVD-ROM, DVD ± R and DVD made of glass (HLD) at high temperature and humidity (Study report 2010 - 1,8 mB)
Durability of recordable DVD±R and DVD made of glass (Syylex) at elevated temperature and humidity (R&D report 2012 - 1,1 mB)
Methods of CD-R and DVDR analysis have been developed at LNE in order to study thoroughly the nature of the defects that produce errors when decoding the HF signal. Often the measured error rate is not correlated with any of the current parameters issued by the analyzers. The developments concern the analysis of the histogram of the positions of transitions towards the clock ticks and the study of parts of the signal such as the beginning of a frame. With these new tools, different types of defects have been highlighted on CD-R. One of them consists of micrometer-sized dark spots appearing spontaneously in the recordable layer during natural ageing. On the contrary, the effect of light is to produce a decrease of the HF signal contrast that is homogeneous over the disc.
See article "Analysis of aged CD-R: From optical HF signal defects to digital errors" published in the journal Measurement.
Laboratoire d'Electronique des Technologies de l'Information
Institut National de l'Audiovisuel
Intégration du Matériau au Système
Latest update: January 2013
Digital optical disks