How do DVD and Blu-Ray compare in durability?

The way Blu-Ray discs and DVDs are constructed may give one a durability advantage over the other, but I lack the expertise to draw a firm conclusion.

Some points: Blu-Ray is higher density, which requires a smaller laser spot when reading. This limits the thickness of the cover layer to 0.1 mm, since a thicker cover would distort the spot. A single-sided DVD uses only half its thickness for recording; I don't know whether this means it's very well-protected from the top or very vulnerable on the bottom, or both. Blu-Ray has a mandatory 2-nanometer hardcoat on the reading side, but the better DVDs have the equivalent. The higher density of Blu-Ray means that damage of a given size will take out more bits. However, Blu-Ray claims to have a better error correction algorithm.

I'd like to compare best against best, which means archival-quality, single layer DVD+R against archival-quality, single layer BD R, so we don't get bogged down in side issues like rewritable discs.

gmcgath

storage
storage-media

Comments

Paul Wheatley: Why do you need to know the answer to this question? Could you expand on how this is of relevance to DP stack? Thanks Gary
gmcgath: My personal need is to improve the quality of the advice I offer in _Files that Last_. Of course, my saying that only bumps the question a level. The broader question is the relative suitability of various media for preservation, but asking the question in its most general form would be too wide-open for this format.
Paul Wheatley: I would argue that neither of these storage types are desirable for long term preservation. I posted an answer on this here, but the question has been closed. Maybe I should re-post here. Not sure what the best practice is for this eventuality

Answer by kvanmalssen

The short answer is: none of these are archival quality. Optical media will be obsolete in just a few years and drives for these are already becoming scarce (my new MacBook Air doesn't have an optical drive!). Optical media also pose digital preservation management challenges as they are limited in how you can provide access, replicate, manage integrity, perform QC, etc. As access copies for designated communities who want and prefer these formats, that's fine. But preservation media they are not.

I would strongly advise against giving anyone the impression that optical media should in any way considered to be archival or suitable for long-term preservation. As digital preservation professionals, we have a responsibility to the public and other non-specialists to demystify this notion that there is something archival about optical discs that manufacturers seems to love to claim. What good is a low error rate if there is no drive to read the content? It seems to be a waste of effort to even talk about these issues, and is potentially extremely misleading.