Researchers at International Business Machines Corp. (IBM) say a new method for cramming data onto magnetic tape will increase storage capacity at least 15 times, enough to squeeze the text from 8 million books onto a cartridge half the size of a VHS tape.

Since high-capacity, reliable hard disk drives are ubiquitous today, tape storage may conjure images of space race-era computers with spinning reels. IBM sold its first tape storage unit in 1952.

But tape is still a common medium for storing materials that aren't frequently accessed, including disaster-recovery files and financial records needed for regulatory compliance. IBM's tape-storage revenue rose 9 percent last year, outpacing the company as a whole.

Scientists at IBM's Almaden Research Center in San Jose, Calif., planned to announce Tuesday that they have invented a process for stuffing 6.67 billion bits into a square inch of tape and 8 terabytes — roughly 8 trillion bytes — on a single cartridge. They contend that would be 15 to 20 times denser than today's industry-standard tape products.

IBM worked with Fuji Photo Film Co. (FUJIY) to change the material that makes up the tape, and also improved the way data can be read and written.

Customers wanting to take advantage of the new tape technology — which is expected to be on the market in about five years — would need to upgrade to new machines.

Also, while each new generation of tape machine traditionally can read cartridges based on the two previous standards, there are no guarantees.

Consequently, customers likely will have to re-record old data onto the new tapes to ensure those files remain accessible well into the future, said David Reine, an analyst with the Clipper Group.