Will Your Records Be There When You Need Them?

Information Management Journal, May/Jun 2006 by Andolsen, Alan A

Changing technology and environmental factors may affect the stability of your digital records. Records managers must schedule regular check ups for their records stored on digital media.

Good records management makes a sharp distinction between backup or disaster recovery processes and the extended retention of digital records. The intent of a backup or disaster recovery is not the retention of information but the ability to restore a computer system in the event of malfunction or disaster. Thus, any digital media created to permit recovery in the case of malfunction or disaster has value for only a short period of time. Current best practices frequently indicate maintaining backup or disaster recovery media for no more than one year or 12 rolling months. After that period, changes in active data or even the system itself may make the data obsolete. The focus here is on the stability of digital media for long-term records retention, not backup, disaster recovery, or business continuity.

In addition, the issues discussed below focus on the stability of the media used for long-term retention of digital records that are no longer maintained on an active computer system and presume that neither magnetic hard disks nor magnetic flexible (floppy) disks are suitable media for the retention of digital records. For stable, long-term retention of digital records, the acceptable technologies focus on magnetic tape and optical disk.

Magnetic Technology

Magnetic tape technology is based on the imparting of a positive charge (a digital "1") to a base metal coating (initially a digital "0") applied on an inert substrate, or underlying layer, of Mylar© or polyester. The positive magnetic charge is not permanent, but begins to fade as soon as the magnetizing field has been removed. The amount of magnetic charge varies with the type of material magnetized. The remaining charge is referred to as the material's remanence. Thus, one of the major goals in choosing appropriate tape media for long-term retention of digital records is to identify a candidate that has a high level of remnanence.

Types of Magnetic Tape

The earliest and best-known magnetic tape has ferric oxide as its base metal coating. Such tapes have been in use for more than 80 years, beginning with audio recording in the 1920s, followed by the first use in data processing in the 1940s, and culminating in the recording of video signals in the 1950s. Ferric oxide tape has been fortified with cobalt to achieve a higher density of information stored on the tape. However, ferric oxide has an inferior remanence that requires planned and repeated recopying of tapes to ensure that the magnetic signal does not fade with resultant loss of data.

The most common magnetic tape in use today has chromium dioxide (CrO2) as its base metal coating. The first use of such tape was for audio because of the greater fidelity of the recordings that resulted from the higher density of storage possible with CrO2. In 1986, IBM chose chromium dioxide for its 34XX family of tape drives. This format has become a de facto international standard for data preservation because of its ubiquity. In addition to its higher density, CrO2 tape has a higher remanence resulting in a much slower signal loss over time. However, it is also prone to corrosion if its environmental conditions are not carefully controlled.

The newest magnetic tape technology uses rare evaporated metals as a base. Among this class of tape are the LTO (Linear Tape Open), DLT (Digital Linear Tape), Ultra High Density, and 359X families. These tapes exhibit an even higher remanence factor and, more importantly, are resistant to corrosion.

Environmental Requirements

Adequate digital records retention mandates strict procedures to ensure that information can be retrieved throughout the authorized retention period. First, to ensure a stable, lasting magnetic signal, magnetic tape needs continuous environmental control.

The goals for temperature and relative humidity (RH) are:

* Operating Environment: 16°C - 32°C (60°F - 90°F) 20%-80% RH

* Storage Environment: 5°C - 20°C (40°F - 68°F) 20%-45% RH

Additional concerns are hydrolysis (absorption of moisture by the substrate causing the metal coating to flake off) and magnetic fields (e.g., exposure to electric motors). In addition to maintaining correct environmental conditions for creating and storing the tape, procedures must be developed to ensure that retention tapes are not exposed to harmful conditions during handling and transporting.

Life Expectancy

All magnetic media have relatively short life expectancies. The effective life of the magnetic media as a retention medium is said to end when an unacceptable error rate occurs during an attempt to read the media. For flexible disks, this can occur within one to three years (thus, the elimination of flexible disks as reliable retention media). For ferric oxide-based tape, the average life expectancy is between five and seven years. Both chromium dioxide and evaporated metal tapes have life-expectancies greater than 10 years. However, to achieve this length of time for a chromium dioxide tape, it cannot be read frequently after recording; otherwise, the magnetic signal quickly drops to unacceptable levels.