The longer we compute, the more electronic history we create. It's amazing how the lowly bytes add up. All of a sudden, we have multi-gigabyte databases.

Another demand is multimedia. Real information is not just names and addresses, it's text, pictures and video. Count your file cabinets. Now, convert every piece of paper to 50,000 bytes. Need a calculator? It's almost as if we've been in the Pleistocene era 'til now (I'm not sure when that was, but it was before electric toothbrushes).

The bottom line is that there's no energy lost or gained in the universe. The 'ole adage -- that if the auto industry followed the computer industry, you could buy a Rolls Royce for $2.50 and get 500 miles per gallon -- is only half the truth. Usage is the other half. If the auto industry had followed us, we'd all be driving a million miles a day.

Following are the trends in tape and disk storage. We're always getting more bytes for the buck, but we can never get enough.

MAGNETIC TAPE

Pundits have prophesied the death of tape for years, but it is stronger than ever. Why? Tape is 25 to 100 times less expensive than disk. Tape cartridges have a 30-year life, and any decent disaster recovery program means you're taking data off site. So while it's not a direct-access medium, it doesn't have to be.

QUARTER-INCH TAPE (QIC)

QIC tape still leads in desktop backup. The venerable 3.5" QIC-80 minicartridge originally started out with 125MB (uncompressed), but has risen to 200, 400 and 500MB with QIC-Wide, Travan and QIC-EX extensions.

QIC-Wide drives support a wider .315" tape. Travan drives support longer tapes as well as QIC-Wide, and QIC-EX cartridges, which come in both .25" and .315" formats, and extend capacity of both old and new drives even further. One company has gone to great lengths to make tape backup simple and cheap. Iomega's $150 "Ditto" QIC-80 Travan drive comes in parallel port and floppy interface versions, and its software makes it a button-click to back up.

There is still action in full-size 5.25" QIC data cartridges. Top models provide up to 25GB uncompressed, but this market is expected to dwindle.

DIGITAL AUDIO TAPE (4MM DAT)

DAT is 4mm audio tape adapted for data. DAT tapes are faster than QIC and hold from 2GB to 4GB, due to helical scan recording, which records data in diagonal chunks like videotape. DAT cartridges are also the smallest modules on the market. Street prices are $900-$1,700, and cartridges run $8-$20, so media cost is cheaper than QIC.

DAT usage is increasing on stand-alones and small to medium-sized LANs. DAT libraries are available that hold thousands of cartridges.

8MM TAPE

Exabyte introduced 8mm tape drives in 1987. Like 4mm DAT, 8mm uses helical scan, and there's more width to begin with. 8mm yields from 2.5GB to 7GB per cartridge. Street prices for drives are $1,500-$2,500 and cartridges about $20. 8mm is faster than QIC and DAT and is used to back up large LANs. Exabyte's Mammoth 20GB system should have been introduced by now and the cartridge price should be in the $30+ range. Exabyte and others make tape libraries that hold thousands of cartridges.

DLT -- HOT STUFF

Last year saw outstanding growth in 1/2" tape cartridge technology called Digital Linear Tape. DLT was developed at Digital and later sold to Quantum, which now OEMs the drives. What's hot about DLT is its raw capacity and speed. A 10GB drive costs about $3,000 with cartridges around $38. Jump to 15GB for $3,500 and $50. DLT libraries are cost-effective too. For example, Overland Data in San Diego makes a 10-cartridge DLT library that holds 150GB for $13,000.

DLT is also faster than 8mm, DAT and QIC, providing up to a 1.5MB/sec data transfer for large backups. DLT is not as