Longevity of DVD-R and CD-R (Was MagTapes)

Teo Zenios writes: I apologize if I am moving this off-topic, but archival longevity of media may be a good topic by itself for the computer preservationist. I have studied this quite a bit. My first conclusion, including that the "100 year" claims we have all seen are baloney. A research article appeared in the German version of Q't magazine (unless I miss-spelled that), where they did some tests on raw error rate on just burned DVD+R media, using some $50,000 equipment. None of the media they tested had a low enough raw error rate to meet the requirements of the DVD+R standard. Yet they sell it. (Mitsubishi did the best.) Then there are many hobbiests looking at raw error rates on DVD media using Lite-On drives with firmware than can report on raw errors. My overall conclusion is that most DVD media on the market sold by no-names, and by the names Sony, Maxell, Memorex, 3M Imation, etc is not very good. These companies re-badge whaterver is cheapest this month from whatever factory. My least favorite factory is CMC Magnetics Corporatioin Europe. Next worst in my view are some Korean and Taiwanese factories (K-Well, In Young, Lead Data Great Quality GQ). TDK seems to be only advertised brand that makes their own and that you can actually buy in a USA retail store, unless the store carries Verbatim. I think Pioneer and Verbatim buy their media from the good Japanese companies, Mitsubishi, Taiyo Yuden, and Mitsumi. Anyway, Pioneer and Verbatim consistently have low raw error rates. A low error rate when freshly burned gives greater margin that as the errors increase as the media ages, error correction can still take care of it. Also, these companies have better engineering about the life span of the organic dyes and such used in the data layer. So when I want it to last, I do this: 1) Use a good burner with low raw error rate after burn/read and good media-to-other-machine cross compatibility. I used to recommend the Pioneer DVR-105 and below, but the DVR-107 and DVR-108 are poor at this. Now I recommend BenQ DW1620 ($52) DVD+-RW double layer drive. Most burners have new firmware you can flash even if you bought it yesterday. A lot of the effort in the new firmware is decreasing the error rate on some media, so it is often worth flashing it. 2) My first choice of media is either Pioneer or Verbatim DVD-R, followed by DVD+R from the same two makers. Third choice brand is TDK. I don't trust much else. Double sided and double layer DVD are a little imature at this point. 3) The freeware Windoze program DVDinfo.exe will tell you who made your mysterious media (reads it off the media). E.g. MCC001 is made by Mitsubishi. 4) All RW media (DVD-RW DVD+RW CD-RW) have poor archival life. Think about it: with RW, instead of burning a pit in the data layer, you are fooling around with glossy or matte finish depending on how quickly a melted liquid re-freezes. Official tests, and my own tests, show poor life. A little sunlight-UV can erase it. 5) I don't burn more than 85% of the capacity of a DVD. DVDs are a sandwich, lexan (polycarbonate) on both sides, data layer chemistry in the middle. The spiral starts on the inside (opposite LP records). If you leave 3/4" unused at the outside edge, it will take longer before the Ozone and 02 and other environmental exposures that attack the data chemistry at the edges of the lexan sandwitch actually reach your data. So on a "4.7GB" disk which in real life could hold 4.3GB, I burn 3.8GB. 6) DVD-R or DVD+R is better than CD-R, because it is a sandwich. DVD also has stronger error correction. CD-R often dies from the label side, by getting bumped against the drive tray, the jewel case, a pen... The paint layer that protects your data on the label side is very thin and fragile. CD-R also die from chemical errosion from ozone, fingers, marking pens, etc on the label side. I write on them only in the center no-data area. DVDs, being a sandwich, don't have those problems. Richard Bristol (the same guy who recently asked for help reading his 9-track mag tapes)