Whoops, There Goes Another CD-ROM
Storing information on disk and tape is convenient, but how long will it last?
The parchment has yellowed and the ink is badly faded, but with a bit of effort one can still make out the words of the Declaration of Independence and the Constitution, penned more than two centuries ago. Both are painstakingly preserved by the National Archives in Washington, D.C., not merely as historic curiosities but, in the words of an official sign, as testimony "to the accountability of a government that lays itself open, through its records, to the scrutiny of present and future generations."
Future generations will be fortunate, however, if they get a chance to view the records of the current Congress, or to look at some 8 million presidential files due to arrive at the National Archives soon after President Clinton leaves office. Most of the documents will be in the form of computer disks, CD-ROMs, and magnetic tapes. And these modern record keepers, archivists and librarians warn, are turning out to be far less durable in many cases than simple parchment.
Tests by the National Media Lab show that top-quality VHS tapes stored at room temperature preserve data dependably for just a decade. Average-quality CD-ROMs become unreliable--some can be read, some can't--after five years. And even when tapes and disks remain intact, the hardware and software needed to read them may no longer be available.
This is a formidable threat, considering that by the year 2000 about three quarters of all federal transactions will take place electronically. Records pertaining to health and human survival--studies of disease transmission, for example, or the location of toxic-waste sites--are of particular concern. The danger extends to the nation's cultural legacy: Virtually all new music, animated art, and early drafts of literature and academic works are created and stored in computers. If such accomplishments are lost, says Deanna Marcum, president of the Council on Library and Information Resources, "we leave an incomplete legacy to future generations."
Part of the problem is that tapes and disks, unlike paper, often do not show degradation until it's too late. Occasionally tapes become so brittle that the magnetic coating actually separates from its backing. More often, however, the signs of damage are subtle: Routine exposure to everyday magnetic fields will rearrange some of the tape's magnetized iron particles. When a machine plays the degraded tapes, these alterations make the tapes unreadable, resulting in missing data. A few years ago, for example, scientists from NASA's Jet Propulsion Laboratory tried to read some of the magnetic tapes that contained the results of the 1976 Viking mission to Mars--tapes that had been carefully stored and appeared to be in good shape. Noting that 10 to 20 percent of them had missing data, one frustrated researcher called the decomposing tapes "a disaster."
Even more troubling than the fragility of storage media, however, is how rapidly computer hardware and software become obsolete. Unlike paper documents and traditional audio and video recordings--which as analog media present a continuous, start-to-finish record of information--computers store data digitally. By breaking information into electronic or magnetic strings of 1s and 0s, digital technology has made it possible to store and access enormous volumes of data using very little space. But without the programs and equipment used to encode it, digital information makes no sense.
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