Evaluation of supporting media

It is accepted today that certain media can no longer be relied upon to preserve electronic files. For example, 5¾ inch diskettes are a very poor conservation choice; their low capacity and inevitable obsolescence make them an inadequate option. And while the inappropriateness of this conservation medium is easy to establish, it is much more difficult to identify the potential of many other current supports and those still to come.  

It is interesting to compare various media to determine those best suited to conserving a given type of file. In this type of evaluation exercise, it is important to consider the criteria that define the medium in question and to measure the relative importance of these criteria.

Longevity

Longevity is a key criterion in the long-term preservation of a work. It is defined as the ability of a medium to last in a material sense while retaining the properties that assure the permanent preservation of the data stored in it. A medium that offers a long, functional lifespan is a better conservation choice than one offering a shorter lifespan.

Stability

The stability of a medium is defined by its capacity to store data in its original state. Magnetic analog tape can become distorted with use, which in turn distorts the reading of data. The data stored on a medium must remain stable; it should not change over time.

Capacity

The importance of storage capacity depends on the type of file requiring conservation. If the file is small, the importance placed on the capacity is limited to knowing whether it is of sufficient size to store the entire file on a single medium. For larger files (video, for example), the capacity of a medium becomes a key factor in any decision made. A larger capacity helps avoid having to compress the file—an action normally required when the file size must be reduced. In fact, it is the large capacity of current media (hard disc, Blu-ray) that today make it possible to reconsider the need to compress files for archiving and conserving electronic media.

Cost

Institutions will continue to spend within their means and look for the most economical solutions. Cost is determined not only by the purchase price of the medium, but also by the subsequent measures that will need to be taken and the considerations involved in the preservation initiative, such as storage conditions, frequency of migration, and equipment that assures ongoing access to the content contained on the storage media.

Fragility

The fragility of components when handled takes on less importance when selecting a medium, because if proper procedures are followed, there is little risk of altering the medium. However, all things being equal, a more robust medium would be a better choice. Rules of thumb include: optical storage media can become scratched or damaged if exposed to light; magnetic tapes are sensitive to magnetic fields; hard discs and videodiscs are at risk if subjected to mechanical shocks.

Storage measures

This criterion allows the complexity of a media storage option to be evaluated. Some media require stricter storage conditions than others, and a museum may have trouble providing these conditions. This criterion also involves assessing the complexity of duplicating a medium.

Commercial popularity

The future availability of a medium depends on its past or current commercial popularity and public appeal. The more popular and widely distributed a medium is, the easier it will be to obtain once it becomes obsolete. The same is true of the equipment used to read and copy the medium. For example, the 3½ inch diskette and audio cassette are still available on the market today, despite having become obsolete.

Risk of obsolescence

While it is often difficult to accurately predict when a medium might become obsolete, curators and conservators should be able to assess the risk of obsolescence for any given medium. For example, Blu-ray discs, which are already having a huge commercial impact, are nevertheless threatened by the accelerated development of new and promising technologies such as holographic discs, which, from a technical point of view, greatly exceed the storage capacity of Blu-ray. Blu-ray is replacing the DVD, which has enjoyed a market lifespan of approximately 10 years. Yet the compact disc, which has been available on the market since the early 1980s, appears in no way threatened by new technology. Many replacement solutions already exist for the CD that are more efficient, but none has successfully taken hold in the music market. The CD has the advantage of being inexpensive to produce, and its technical characteristics more than meet the listening needs of the average audiophile.