Your Linux Data Center Experts

A recent question on the Boulder Linux Users Group mailing list was about CD media failures a member was seeing. I wrote up this response and then realized that it was probably useful to a broader audience.

I have a bit of experience with this, since we burn something on the order of a thousand CDs a month. :-) A couple of things up front though. First of all, drive quality seems to matter more than disc quality. We send out our CDs to people all over the world, and have found that even after we burn and verify discs here, low quality discs have tended to fail on other peoples drives. We've even tested it to the point where we've had people send back discs that were having issues to see if they got damaged in transit, and they verified fine when we got them back. Sending a replacement set to them resolved it though.

And by “better drive” I'm not talking cost, our burners are mostly fairly cheap drives. I'm not advocating you all go out and buy Plextor drives, I haven't really had that good of luck with the ones I've had in the past. We mostly are using Mitsumi and TDK drives here and have been happy with them.

The other thing is that just because you can read it doesn't mean that it's a good burn. Some marginal sectors the drive may be able to read after spending many seconds or minutes trying hard at it. IMHO, that burn is “bad”, it's just asking for trouble to rely on data on these, because as the discs age these marginal sectors are likely to become hard to read faster than the rest of the disc. Your data integrity is only as strong as it's weakest track, and all that jazz…

Now, on to media quality… We had one drive that would reliably fail on discs that our customers had problems with. If we verified every disc through this drive, we could be pretty sure that all our customers could read them.

Around the time we were having these problems, I came up with a new verification program which was much stricter about what it considered a “bad” disc. In our next burn cycle, we used this verification system and discs we had from a fairly large manufacturer were showing 50% failures. At first I worried that the verification system was having problems, but I double checked it twice :-) and it seemed to be working as expected. We switched to using Taiyo Yuden discs, and since then have had absolutely no problems.

Those discs were about twice the cost of the other discs, but with a 50% failure rate, it was actually cheaper to use the more expensive discs. Our customer complaints about CD failures basically dropped off to nothing at that point.

So, there IS a difference in disc quality. I've seen it, absolutely. I've had absolutely fantastic luck over the last 2 or 3 years with using Taiyo Yuden discs. If I had something important to store, that's all I'd use.

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