If the 10 Commandments had not been lost sometime between 600 and 586 B.C., we could likely still make out the ancient words on the two stone tablets.
But if Moses had transcribed those edicts onto CD-ROM, diskette or magnetic tape, they would have been gone long before the Ark of the Covenant itself disappeared.
Although the modern world is committed to the digital storage of everything from Social Security records to Pearl Jam records, no one knows exactly how long the stuff will last.
Though the field of digital data storage is only a few decades old, scientists can come up with pretty good guesses about the life expectancy of various media through artificial aging tests. This sort of testing is done at the National Media Laboratory at 3M Co. in Minneapolis, a project of industry, government and university researchers.
John Van Bogart, the lab’s data preservationist, says several media samples are placed in excessive temperature/humidity/pollutant environments, then removed at periodic intervals for measurement of key properties, including physical characteristics and data error rates.
Testing has determined that magnetic tape has a life expectancy of 10 to 30 years, diskettes about 30 years and CD-ROMs about 100 years.
In practice, it turns out, the lifespan of individual media may not be as important as it seems: Government and business are constantly practicing a juggling act, moving data to new disks and tape, and reformatting data to keep up with current common applications.
And for long-term storage, there’s always the old-fashioned way.
For the typical checking account customer at First National Bank of Chicago, banking transactions are stored for a short time digitally, then long-term in an analog medium.
“We keep on the mainframe the current month’s information and three months back. We have tape backups; some we keep on site, some we keep off site,” said Thomas Kelly, First Chicago vice president.
Once banking information is four months old, it is put on microfiche. So if a customer wanted to see the statement from March 1995, the bank could pull that analog record.
So if the computers at your bank should mysteriously crash and burn, the bank will still know how much you owe on that home loan.
“In a worst case, we could go back to information that is 23 hours old. If it’s updated daily, it’s never more than 23 hours old. We regularly test for that,” Kelly said. And with backup tapes in a different location than branch offices, even fire and flood won’t keep banks from business as usual.
For such crucial data as Social Security records, the preferred method of storage is disk. But your records aren’t on the same disk all your work life.
“There is no fear of losing information,” said Lovell Brigham, spokeswoman for the Social Security Administration. “It might be a matter of just transferring information to a different format, upgrading disks. We are constantly changing, keeping up with the latest technology, and as well have built-in redundancy systems.”
So the system is designed to last forever?
“Exactly. If we need information from 1940 or 1960 or whatever, we’re able to retrieve the information,” Brigham said.
At Chicago’s Goose Island Beer Co., everything is digital, and backed up on tape at least once a day. But it’s not only digital.
“Of course, we still have paper records,” said Tony Flores, an accountant for Goose Island. “Sometimes you need to verify signatures, what the actual information is. And occasionally when entering data, it’s always possible to make a mistake. Paper is the final authority,” he said.
For First Chicago, Kelly says, paper is rarely an option. “Banking and insurance are the two most systems-dependent industries. Almost everything you do at the bank is in computer now,” he said.
For example, payroll accounts generate virtually no paper.
“You would get a piece of paper from your employer, but we would get a tape that would have the entire payroll information on it. It would be sent over every two weeks with all of this information. You get a paper record of your paycheck, but in fact there’s not any paper that changes hands from the (employer) to the bank,” Kelly says.
The storage medium is not the only factor in the longevity of the message. Also important are the format of the data, the integrity of the recording appliance–that is, how likely it is to fail–and the life expectancy of the recording medium for playback.
The integrity of the recording appliance can be a large factor in how long the information will remain viable, so data is regularly transferred to newer media and saved in new formats.
The regular migration of data to new formats is a necessary safeguard and a “huge operating expense” for business and government, said Abby Smith, program officer at the Council on Library and Information Resources. She estimates costs in the tens of millions of dollars for the biggest, most data-intensive firms.
“Migration is a necessary part of preserving digital information,” the media lab’s Van Bogart said. “Even the best medium will not last forever. You may be able to use it for 20 or 30 years, then the medium will start to deteriorate and there will probably be something better out there technologically.”
