The most common strategy for backing up a hard disk drive is to copy files onto a series of diskettes.
Well, not quite. "The most common strategy is to not back up at all," noted James Porter, who analyzes the hard disk drive industry for Disk/Trend Inc. of Mountain View, Calif., a market research firm.
But "for those who are prudent about the way they approach life," Porter said, diskettes are indeed the most popular backup medium. Almost every personal computer comes with at least one diskette drive.
Diskettes are relatively cheap, and they can be locked in a desk drawer or stowed in a briefcase.
The problem is that hard disk capacities, measured in millions of characters, or megabytes, have increased much faster than floppy diskette capacities.
The de facto standard for new computers is a 40-megabyte hard disk, but 80-, 120- and even 200-megabyte drives are increasingly popular. The standard floppy diskette capacity, however, is 1.44 megabytes.
Even with a technique known as file compression, which can pack the proverbial 10 pounds of data into a 5-pound bag, it can take a pile of diskettes and lots of time to copy the contents of a big hard disk.
There are faster and more efficient ways to make large-scale backups, including minicassette tape cartridges, removeable hard disks, disk mirroring, portable hard disks, digital audio tape, eight-millimeter tape and "floptical" diskettes that can store 20 megabytes of data on a single diskette.
Minicassette tape cartridges are increasingly popular for personal computers, especially after a round of price cuts last year that drove prices as low as $200.
These tape drives are small enough to fit in a standard computer disk bay, just like a diskette drive, and they can quickly copy as many as 250 megabytes of data onto a single cassette the size of a pack of playing cards. Most major backup programs now work with tape drives as well as with floppies.
Big computers have had tape drives for many years, but tape is relatively new for personal computers.
The three most common types of tape drives for the PC set are QIC 40 (for quarter-inch cassette 40-megabyte), QIC 80, and the Irwin format, a proprietary system made by Irwin Magnetic Systems Inc. of Ann Arbor, Mich., a division of Archive Corp. QIC drives are made by several companies, including Archive and Colorado Memor Systems Inc. of Loveland, Colo.
The basic drives are rated for 40- or 80-megabytes of storage, but by using longer tape and file compression software, which is usually included with the tape drive, capacities are effectively tripled to 120 or 240 megabytes. Most people can dump their entire hard disk contents onto a single cassette, and data transfer rates are faster than on floppy drives.
If you consider the time it takes to feed dozens of floppies into a computer during a backup, the cost of a tape drive -- typically $250 and up, depending on capacity -- is a bargain. The cassettes themselves cost $20 to $30, again depending on capacity.
"Tape is popular because it is a mature technology with proven reliability and lower cost," said Robert C. Abraham, vice president of Freeman Associates Inc. of Santa Barbara, Calif., a management consulting firm for the data storage industry.
Other technologies, including digital cassette drives, digital audio tape (DAT) and eight-millimeter tape drives, are more expensive, but they offer storage capacities measured in gigabytes (billions of characters), according to Abraham of Freeman Associates.
For offices that have several PCs, Valitek Inc. of Amherst, Mass., makes a portable tape cassette drive that simply plugs into the computer's parallel port. The Valitek drive is "non-invasive," meaning that it does not require installing any internal drives or circuit boards, and it does not alter the target computer's system software, as other backup systems often do.
In other words, the Valitek drive is like a hand-held vacuum cleaner that sucks out a copy of the hard disk's contents onto a cartridge.
The data can then be transferred to another system or stored on a digital cassette or tape cartridge, depending on the model of the Valitek drive.
A 60-megabyte Valitek system has a list price of $1,595. A 160-megabyte system is $1,845, and a 250-megabyte system is $2,095. The prices seem high, but the cost is typically shared by many users.
Another popular alternative is a Bernoulli drive, made by the Iomega Corp. of Roy, Utah. A Bernoulli drive uses a 5.25-inch removeable disk, much like an overweight floppy, that can store as much as 90 megabytes of data. The drive itself has a list price of $1,149, which includes one 90-megabyte cartridge; extra cartridges cost $229 each in packs of three.
The Bernoulli drive combines the high capacity and speed of a hard disk with the easy portability and reliability of a diskette. For people who want to swap large projects in and out of a computer, or to share large amounts of data with colleagues just by handing them a fat floppy, the Bernoulli beats tape.
Unlike conventional hard disks, which are subject to "head crashes" that can damage the magnetic surface of the disk, Bernoulli disks float on a cushion of air.
In the event of a power loss the disk falls away from, not into, the delicate read-write head.