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At 08:28 AM 3/25/2005 -0500, Anonymous SET ARSCLIST DIGEST wrote: >In his post Dave Nolan said, > >...writable CD/DVD copies are turning out to have SO many problems with >longevity past 10 years that it seems that they are NOT good long-term >archival storage media. > >Could you please elaborate on this. We are essentially without data on longevity and even readability of media. To some extent that is because hardware, formulations and manufacturing processes are changing faster than testing can be done. Another factor is that we lack viable test tools - particularly since validity of accelerated life test is not quantified. Yet a third is the lack of incentive for the manufacturer to establish those data, A fourth is that most media are rebadged so that one has no consistency from one purchase to another. That said - and recognizing that we have no more hard data on what follows than on what went before - the most common reason for failure of a disc is that it was poorly written to begin with. Poor writing is usually due to mismatch between properties of the writer and the medium, especially at the chosen speed. Thus, although a modern drive capable of writing at 24x will write at 4x, whether the blank in question is capable of only 4x, 24x or 52x there is a good chance that that drive and that blank written at 4x will give poor results. It would be wonderful to have a modern drive and modern medium optimized together for writing at moderate speed; to have that combination made available by a reliable vendor who could give assurance of compatibility; and to have certification of some sort on at least the quality of result that would obtain. Don't hold your breath for such a vendor or for affordable product from him. I have heard from many and tend to believe it true from my own results that as fine a CD recorder as has been marketed to date is the Plextor 8x writer (either model), particularly with SCSI interface. There is no doubt that for archival purposes a caddy drive is wonderful protection for writing and reading. As far as I know, the companies producing such hardware have either dropped those lines as having no market or have gone out of the business altogether. For quality results, it is essential that the quality of write be established for your writer(s), medium and speed. Properly, that should be done with a battery of tests of the sort done by Media Sciences. For practical reasons, BLER test equipment may be sufficient. Because I am an amateur little concerned with longevity beyond my own lifetime, I find error-rate tests with Infinadyne's Diagnostic and Inspector programs sufficient; even the freeware CDSpeed will do the job adequately for some. The bottom line is simple, though. A well written disc will read in any modern player. It is true that error rates for shorter blanks are substantially lower than those for longer ones and that errors tend to be substantially more frequent toward the circumference of the disc - later in the recording. But a well written "80-minute" disc will be more easily read and will last longer than a poorly written 74 or even 63 (are they even produced any longer?). The similarities between recordable CDs and DVDs are more significant than their differences, especially in -ROM applications. There is a complication if you choose to write DVD-ROM on DVD+R - a bit which must be set correctly for consistent reading. (I would appreciate it if someone knowledgable on this would share specifics.) Otherwise, we have the same ignorance of longevity, the same lack of correlation between package marking and contents, the same issues of rebadging and consistency on the two media. Fortunately, we also have the same ability to quantify write quality and the same reason to hope that a well written disc will outlast one written poorly. Mike -- [log in to unmask] http://www.mrichter.com/