Somewhat surprisingly, according to Alex Johnson, product manager, Loronix, Inc., a company that designs and markets digital video imaging and CCTV surveillance systems, most of their entry-level clients, like the above convenience store, are still using VCR recorders and eight-hour tapes, which get changed every shift. For that matter, many high-end clients, such as casinos, are as well. A typical casino, for example, may have 2,800 cameras feeding into 700 VCRs, with tapes swapped out each shift, and moved to a vault for a mere week. "If the casino wanted to store say 2,000 cameras, 14 days, at real time, you're looking at 3PB of storage," says Johnson. "That's an insane amount of video."

But what if there's an incident and it needs to be found on the tape? If you're th...

Avoiding that is one reason some customers now use digital video recorders, which take an analog signal, digitize it, compress it and store it on a local disk drive resident to the recorder.

Many of Johnson's clients are also keeping images for longer periods. "We have a large customer that has 200 locations worldwide and they store locally at each of these sites. But whenever they have an 'event,' they ship it back to a centralized tape farm at their headquarters, where they store--long term--only the relevant info."

Tape, not disk, is these customers' long-term storage media of choice. "If you think about the cost per GB for a high-end disk storage device that will store 30TB of data vs. tape, it's significantly less expensive," says Johnson. "Assuming reliability is equal, the only factor is retrieval time. So, if I'm looking for a piece of data that's four months old, am I going to be willing to wait a few minutes? Not a big deal."