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Post Database

By Thiravudh Khoman

In the January 20, 1999 issue of Post Database, reader Tony Dabbs wrote about having problems reading certain CD-RW disks on his Ricoh CD-RW drive. Unless I'm mistaken, the Ricoh drive comes with Adaptec's DirectCD program (which is needed to write to CD-RW's) and the standard version of Adaptec's Easy CD Creator (which is used to write data and music CD-R's).

It should be noted that in the past year or so, DirectCD has been updated at least a half dozen times. Thus, reader Dabbs should download and use the latest version of DirectCD (v2.5c, as of this writing) from Adaptec's website at https://www.adaptec.com. Also, if he hasn't done so already, he should register his Adaptec software online, whereupon a nice lady named Deirdre Straughan will email him whenever a new software update is released. Meanwhile, it wouldn't hurt to browse Adaptec's plentiful technical bulletins which might provide additional hints as to his problems.

Finally, there's the low-tech approach: find someone who has a CD-RW drive and try to read and transfer the problem CD-RW's to regular CD-R's. Of course, this is easier said than done, since CD-RW drives are still hardly ubiquitous.

CD-R's Better?

Having said all this, I'd now like to make the extraordinary recommendation that reader Dabbs avoid using CD-RW disks altogether! I've been using an HP CD-Writer 7100i drive for part of a year now. Aside from HP's excellent reputation, I especially liked the drive's ability to handle CD-RW's. Just think about it - the equivalent of a 500mb floppy. Fantastic!

Yet when I started using CD-RW's in earnest, I found its shortcomings too high a price to pay. First of all, CD-R's and CD-RW's destined for use with DirectCD need to be formatted the first time they're used - a time consuming process. Second, CD-RW's cannot be read on many CD-ROM drives, especially older models. This will limit the number drives you can transport your CD-RW's to, a risky predicament if your own CD-RW drive were to break down.

Finally, there's the matter of cost. CD-RW's are significantly more expensive than regular CD-R's. In the realm of high quality CD's (e.g. HP, Kodak, Sony, etc.), CD-RW's typically cost about 10 times that of CD-R's made by the same manufacturer. In the lower grades the price differential is less, but still a 4-6x price difference isn't unusual.

While I can grudgingly live with the need to format CD-RW's, the lack of portability and the high costs seriously crimped my style. I found myself using regular CD-R's more and more as they had none of the aforementioned problems: no prior formatting, a high degree of portability, and cheap, cheap cost. While I started out with brand name CD-R's, I eventually gravitated to lower priced CD's. So far, I have experienced no problems attributable to the lower-quality CD's, although I have tried a half dozen brands and am now on my second "century" of CD-R's. My latest batch of CD-R's costed Baht 40 per CD-R in batches of 100, which is a far cry from the Baht 800 price tag for a single HP CD-RW.

I can also live with the chief drawback of using CD-R's versus CD- RW's: the fact that you must use a special purpose program to write to CD-R's (I use Easy CD Creator Deluxe v3.5) (figure 1), unlike CD-RW's where you can use Windows Explorer, DOS, or the "Save" command of practically any software program. Fortunately, Easy CD Creator's interface is similar enough to Explorer so there's not that much of a learning curve, and it also allows you to save "layouts" for frequently used backups (similar to what most disk backup utilities have).

Multisession CD's

I've saved the best feature of CD-R's for last: practically all modern CD recorders can write what are called "Multisession" CD's. while the surface of CD-RW's can be written to and erased a multitude of times, each section of a CD-R can be written to only once, but read many times. Back in the early days, once a CD-R is written to, it had to be "closed", never to be written to again. Run into a problem like a data over-run or under-run (i.e. the computer sending data to the CD writer too quickly or too slowly) and the CD becomes unusable and has to be thrown away.

These days, once a CD-R is written to, additional data can be added to the CD as long as the CD is not "closed". This is done by writing a new "session" to an unused part of the CD (figure 2). A CD-R can hold many sessions (I'm unsure of the theoretical limit), each of which are effectively self-contained and invisible to each other. Thus, you can write five generations of a file named X56.DOC to five different sessions, and be able to access each of the files individually. In fact, you can keep using the CD until all available space on the CD used up as long as the CD is not closed.

(I hate to disappoint you, but you probably can't use the unused space on freebie CD's, Panthip CD's, or obsolete commercial CD's. These CD's are "pressed" using a different technology.)

The important thing to remember here is that only the last session is considered the "active" session. Indeed, take a multisession CD to a regular CD-ROM drive and all you'll see is the LAST session (although with VERY old CD-ROM drives, all you'll see is the FIRST session - i.e. these drives don't support multisession recordings). To access prior sessions, you need a session selector type program (Easy CD Creator Deluxe has this), and to "activate" whichever session you desire. Once activated, you can access the files in that session until you activate another session, write a new session or remove the CD from the drive (i.e. the "Cinderella Effect").

Another great feature of multisession CD's is that you can "import" data from previous sessions without wasting additional space. For example, if you had a 100mb database file in session 1 and wanted it to be visible/useable in session 3, simply import your session 1, remove any unneeded session 1 files, add any new files, and then save the session. The space requirements for session 3 will depend only on the new files added and some space to write a new file allocation table (all sessions have their own independent FAT's). In other words, that 100mb database in session 1 won't waste another 100mb in session 3.

What I'm hinting at is that multisession CD's are ideal for making backups, as long as your data isn't too large. If reader Dabbs uses a single CD-RW to back up a year's worth of data, he could equally well afford to buy 5-10 CD-R's to back up several generations of data on those 5-10 CD's. If one CD were to go bad (unlikely in the short run, but always a possibility), he'd always have others. As long as each sequential backup is made on another CD and not lumped together on a single CD, or if duplicate CD's are made, a recent backup should always exist. On the other hand, misplace a single CD-RW, scratch it, have Windows give it the kiss of death, or ... you get the picture. Safety first: don't put all your eggs in one basket.

Copyright © 1998-2000, Thiravudh Khoman