Longevity of DVD-R and CD-R (Rewrite from original poster)

I am the scoundrel that made the original post on this topic that opened a flood of discussion. Members brought up details that I never addressed; and I learned from everyone's posts. Thank you! This may be useless, beating a dead horse, and off topic. I am re-submitting here my original 6 point comment with corrections and links, and with ADDITIONS as points: 7, 8, 9, 10, 11, and 12 to cover other areas people have brought up, etc. Richard Bristol ---------------------------------------------------------- Archival longevity of DVD and CD media may be a good topic for the computer preservationist. I have studied this quite a bit. My first conclusion, including from crude accelerated life and torture tests I made myself, is that the "100 year" claims some people made are likely 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. For example, hobbiests measure and post on sites like: http://www.cdrinfo.com/Sections/Reviews/Print.aspx?ArticleId=11657 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 Corporation in Europe. Next worst in my view are some Korean and Taiwanese factories (K-Well, In Young, and Lead Data=Great Quality=GQ). TDK seems to be the only advertised brand that makes their own DVD-R that you can actually buy in a USA retail store (although one member said maybe they don't make it themselves), unless the store carries Verbatim. I just verified that Pioneer and Verbatim buy their media from the good Japanese companies, Mitsubishi (MCC), Taiyo Yuden (TY), and Mitsui. 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. 7) If you really care about it's archival life, hedge your bets by burning two copies, on DIFFERENT media. Select two good media types made by different companies. Each may have, just a guess, a 10% chance of self-destructing within 20 years. This would be because of a design or implimentation mistake. For example perhaps the sandwich adheasive includes a chemical that eventually reacts badly with the data, or some impurity in manufacturing at that time. If the two media are very different, their probabilty of failure approaches statistical indpendence; and if independent then the chance that both are unreadable would approach 0.1 * 0.1 or only a 1% chance. 8) Because the data is sandwiched in plastic, my belief is that single-layer single-sided DVD-R or DVD+R as a class will last longer then CD-R as a class. However, some applications require CD-R. For archival CD-R I have used extensively and can recommend "BASF by EMTEC" (Emtec in USA) "Ceram Guard" CD-R BASF CD-R74 Maxima Ceram DA (really made by Taiyo Yuden). (Beware some different Emtec/Basf CD-R are made by CMC and are poor.) However "Ceram Guard" is truely hard to buy in the USA. I bought mine for $2 each from the retail chain "Guitar Center" in person (guitarcenter.com). They were marked "for audio use" but that does not matter. They are NOT gold. Their feature is that a ceramic coating is vacumn sputter-coated on the labeled. You could probably use a ball point pen on it. They are by a mile the most sturdy CD-R I have ever seen. Unlike most CD-R, taps to the label side don't kill them. Out of about 1000 CD-R I have seen or used "in the field", I have seen about 25 dead CD-R's (that were once good) And 22 of those 25 were at least slightly abused. (Sun, moisture, tap on drive tray on label side when inserting, or tap on jewel case) Only 3 of 25 appeared to die from purely with "from the inside bit rot". Of those 3, 2 were made by one company: GQ Great Quality, Taiwan. So I am mostly interested in the label side coating. These ceramic coated disks are mentioned here: http://www.cdmediaworld.com/hardware/cdrom/basf.shtml BASF/Emtec also sells these as "archival" but I would want to know who made it for them before buying. They are real gold: BASF/Emtec CD-R Gold Digital Photo BASF/Emtec DVD+R Digital Video Gold Occasionally you can find "Kodak InfoGuard". They are expensive. They have a very tough label side, and use gold. They are semi-discontinued, and were sold to medical and business markets. If you have a Kodak "Picture CD" from film processing you may have one there. Kodak digital science InfoGuard, maker: Kodak Japan Limited, Phthalocyanine 1X - 4X Kodak Gold Ultima InfoGuard, maker: Kodak Japan Limited, Phthalocyanine 1X - 4X More practically speaking, you CAN actually buy Mitsui "MAM Gold CD-R" for about $1 each now. They use real gold, and have a decent paint layer they call "diamond coat". (But it's not anywhere near the toughness of "Ceram Guard" or even "InfoGuard".) Described for sale here: http://store.mam-a-store.com/standard---archive-gold.html 9) I don't know if high-spin readers contribute to media death. But too high a speed definitely contributes to "can't read Table of Contents" and "ECC Error" on read, and marginal quality burns. Plextor CD-R burners come with PlexTools(?) software specifically to slow them down. You can sometimes read a CD-R this way that otherwise can't be read on newer faster readers. To read a CD-R whose errors are too high for most all readers, I prefer these to read it: Plextor 4x CD-RW drive, or 12x (not 8x). Plextor 20x and above are not as good. Cheap and I have a few: Panasonic 12x just plain reader. Sometimes other 4x readers by NEC, Panasonic, Pioneer, Sony. 10) I like to try, when burning, for the lowest raw-error-rate (that some machines can tell you when you read). Published tests show excessive speed hurts. My rule of thumb when burning is: Never exceed the lesser of the media's rated speed, or 2/3 of the burner's maximum speed. So if a CD-R burner will burn at 48x, and the media says it is 80x, I will burn it at around 12x or 24x. There is such a thing as too slow also, for a particular burner. The sweet spot gives you a lower raw error rate, and greater cross-compatibility when reading it on many different drives. 11) A disk that takes a long time to "settle" (usually light goes out) on insertion is a possible indication of a high error rate and likelyhood of complete table of contents failure later. 12) The free Windoze program md5summer.exe will generate a text file with .md5 ending for any directory tree of files. Each line in the file is the md5, a space, *, and then the pathname; one line per file. I put one of these .md5 files in the top level of my CD-R or DVD-R burns. Then, in Windoze a couple years later, double click that .md5 file and it does the opposite, and confirms the md5 of each file on the media. I have seen a few CD-Rs that were damaged, that in Windoze gave no error message at all when read, but the data read back was actually wrong. I use md5summer also before ftp etc. transfers. Will someone better informed say how this is best done and commonly done in linux and unix? Perhaps find . -exec md5sum '{}' \; > md5sum_list or something? And the checking later? Richard Bristol (the same guy who recently asked for help reading 9-track tar tapes)