Letter To The Editor: A question answered

Question:

I am constantly seeing the DVD drives advantages to imaging but not seeing anything about the down sides. For example, what about the seek times for a device that uses a concentric single track and not the multiple tracks of CDs or laser disk data. --Scott Anderson

An answer:

Are DVD access times fast enough for imaging? The short answer is: don't worry about it. The long answer is: CD and MO are still the disks of choice and nobody's yet worked out how DVDs will be used in imaging systems.

Replicated CD-ROMs and recorded CD-R disks are very attractive storage media for large imaging files not because they are capacious--even 650 MB doesn't seem like much these days--but because they are inexpensive. They're almost ideal for sneakernets, jukeboxes/towers and other data distribution schemes where transporting disks is more cost-effective than transmitting their contents electronically.

Moreover, you don't need a recording drive to read CDs, and a read-only drive costs less than $100. Even the fastest read-only drives cost less than $400. It's almost impossible to buy a computer nowadays that doesn't have a CD-ROM reader or a multi-disk changer in it. The fact that the recorders are getting cheaper--$500 in bundles and even less as bare drives--further adds to the appeal and the longevity of CDs as imaging storage media.

But as the reader points out in his query, CDs are linear media: their data is recorded in a helical track starting at the hub, which can stretch out access times especially where files are small and/or widely separated on the disk surface. For applications that demand fast access times--as well as higher per-disk capacity--CDs do not compete well against 5.25-in. MO optical disks, which are recorded in "track-sectors" and so can achieve truly random file access.

DVD recording is not yet standardized across all manufacturers, though there is general agreement that it will be done in track-sectors, which implies fairly fast access times. But don't hold your breath for turnkey systems.

The first DVD players are also out. They cost $700 or so, but there isn't even much replicated software yet; phone directories are about it for now. Real business applications need sophisticated software and end-to-end hardware support comparable to what's available in turnkey MO- or CD-based imaging systems, neither of which is in the market yet.

True, the first DVD recorders are available, but in limited quantity, and they are impracticably expensive. They retail for more than five times the price of MO drives, yet they store only 3 to 4 GB, which is not significantly different from the 2.6 or 4.3 GB that MO drives offer today; and it's less than the 5.2 GB MO capacity that is almost certain to arrive by early 1998.

MO and CD have another crucial advantage: they've been around long enough for manufacturers to offer backward compatibility. With the unfortunate exception of the new erasable CD-RW, all CD readers can read all CD disks. Nobody today is guaranteeing that all DVD readers will be able to read all recorded DVD disks.

I expect that the much-hyped dual-sided and/or dual-layered DVD recorders, capable of holding 9 GB or more, will come with a comparably high price tag whenever they emerge-- which won't be until well into 1998 or possibly 1999.

So I don't think we'll see a commercially viable DVD-based imaging system soon, at least until recording costs fall to the level of MO. And until then, access time issues are moot.

--Hal Glatzer, IW contributing editor