WHY ANALOGUE?
Lowest recurring costs
Because the readability and lifetime of electronic storage media is endangered due to technical obsolescence, electronic digital storage systems have to be reformatted and copied onto new media every five to ten years (migration). Consequently, digital data storage leads to high recurring costs.
The National Archives and Records Administration has published cost estimates for image preservation. The estimate for the preservation of digital image files worked out to recurring costs of $ 17 / GB / year or more [1].
The Harvard University Art Museum’s photography studio made a complete transition of its film vault to digital several years ago. When deposited to the Online Computer Library Center storage cost was $ 15 / GB / year versus a roughly two hundred times lower cost of about $ 0.07 / GB / year for storage deposit in the film vault before [2].
The National Archives in Stockholm have invested in a 200 TB tape cassette robot system several years ago. The cost estimate for the system and its operation lead to recurring costs of about € 3 / GB / year [3].
The cost levels of hard disk and tape based storage at the San Diego Supercomputer Center with 25 PB storage capacity have been published recently. The running cost was about $ 1.50 / GB / year for hard disk and $ 0.50 / GB / year for tape based storage [4].
All of the above mentioned reports on the cost levels for digital image retention lead to the following conclusions
- Institutions will only be able to justify the retention of digital image data that is frequently used , e.g. accessed online
- Institutions will need to perform a cost-benefit analysis to determine how much digital image data can be provided online
- Image preservation on microfilm requires no migration for up to 500 years
- Microfilm is by far the least expensive preservation medium
- Hybrid approaches, using analogue and digital technologies to its best advantage, are likely to be most viable.
Literature
[1] The Costs of Digital Imaging Projects. By Steven Puglia, RLG DigiNews, Vol. 3, No. 5 (1999).
https://chnm.gmu.edu/digitalhistory/links/cached/chapter3/link3.10b.digitalimagingcosts.html#feature
[2] Counting the Costs of Digital Preservation: Is Repository Storage Affordable? By Stephen Chapman, J. of Digital Information, Vol. 4, No. 2 (2004).
https://journals.tdl.org/jodi/index.php/jodi/article/view/100/99
[3] The Digital Black Hole. By Jonas Palm, Swedish National Archives, Stockholm (2007).
http://www.tape-online.net/docs/Palm_Black_Hole.pdf
[4] Disk and Tape Storage Cost Models. By Richard L. Moore, Jim D'Aoust, Robert H. McDonald and David Minor, Proc. IS&T Archiving, p. 29 (2007).
