Optical Data Storage

© ISO Focus, www.iso.org/isofocus

Main Focus

ISO standards for optical discs are interchange and storage – Data migra- Optical data developed within joint technical committee tion method for DVD-R, DVD-RW, DVD- ISO/IEC JTC 1, Information technology, RAM, +R, and +RW disks, was published storage – How subcommittee SC 23, Digitally recorded in February of this year. long will it last ? media for information interchange and Together, these two standards pro- storage. Until relatively recently, SC 23 vide a reliable system for DVD archiv- focused exclusively on specifications for ing applications. interchangeability of media, developing By following ISO/IEC 10995, users by Yoshinobu Mitsuhashi, Chair, standards for technologies such as CD- can select high-quality DVDs with a short ISO/IEC JTC 1/SC 23, Digitally ROM and various types of DVD. practical measuring time for an archiv- recorded media for information ing system. Users are advised to measure a specified initial recording performance interchange and storage “ The number of optical disc according to ISO/IEC 29121. Discs for n just a few short years, DVDs have drives sold worldwide in data storage should be checked period- become the most successful consumer ically with the test frequency described 2007 is estimated to be in in the standard. Ientertainment product in history, quick- excess of 550 million.” ly eclipsing the earlier success of video- tape and compact discs. But their popularity is not confined Users are, of course, constantly to consumer electronics. Optical discs seeking media with higher capacity and also play an important role in the profes- higher data transfer rate. In particular, how- About the author sional digital universe, and now dominate ever, there is a growing demand for archi- both markets. The number of optical disc val digital data and increasing concerns Yoshinobu drives sold worldwide in 2007 is estimat- about the archival life of optical media. Mitsuhashi, ed to be in excess of 550 million, with a In response to market demand, ISO/IEC Chair of ISO/ market value of USD 21 billion. JTC 1/SC 23 has begun to address data IEC JTC 1/SC archiving issues. 23, Digitally recorded media A new need arises for information Reliable system interchange and Standardization of optical discs storage, gradu- In this respect, ISO/IEC 10995, was first discussed at the Topical Meet- ated from Tokyo 1) Information technology – Digitally ing on Optical Data Storage of 1983 , Institute of and the first ISO technical committee recorded media for information inter- Technology in 1964 and joined Electro- plenary on the subject was held in 1985, change and storage – Test method for technical Laboratory (now Advanced with participation from researchers, engi- the estimation of the archival lifetime of Industrial Science and Technology). neers and technocrats from industry and optical media, was published in 2008. It Since then he has studied optical academia. provides a simple method for estimating information processing. In 1983, the useful life of DVDs. Dr. Mitsuhashi became active in 1) Sponsored primarily by the Optical Society A further standard, ISO/IEC standardization of optical discs, and was of America (OSA) and IEEE, professional 29121:2009, Information technology – head of the Japanese national mirror association for the advancement of technology. Digitally recorded media for information committee for ISO/IEC JTC 1/SC 23.

26 ISO Focus April 2009 © ISO Focus, www.iso.org/isofocus ISO and the Media

If the recording performance is within a specified level, the disc is clas- sified into one of three categories : • Suitable for continued use • The data on the disc should be migrat- ed to another disc as soon as possi- ble • The data on the disc should be cop- ied to another disc immediately to the extent that the data can be retrieved.

Essential steps for longevity The typical life of an optical disk is said to be 30 years, but in reality that may be anywhere from one year to a cen- tury or more. In a recent US government survey of 4 483 users, a majority consid- ered archival longevity of more than 40 years to be important 2). While the industry can supply discs of high enough quality to survive for 40 years, disc drives gen- erally cannot meet that standard. For this reason, users should change drives peri- odically as technology advances. “ Together, these two standards provide a reliable system for DVD archiving applications.”

For archival optical disc applica- tions, it is essential not only to select a quality disc, but also to migrate data on the disc periodically. In 2008, a non-profit organization, Archive Disc Test Center 3), was established in Japan to estimate the useful life of optical discs. ISO/IEC JTC 1/SC 23 will continue its discussion of the necessity of standard media and standard drives to further promote archival optical disc applications.

2) Optics & Photonics News, May 2007. 3) www.n-adtc.org.

ISO Focus April 2009 27