HD failure rates are higher than DVD because the hard drives are spinning 24/7 in most computers. DVD's wouldn't last long if they were continually spinning and accessed 24/7.
How long have DVD's been around? The Optical Storage Technology Association has a
blurb informing that most of the longevity test are based on CD's. There's also a difference between commercially pressed media vs home burning of DVD media.
The advantages you list are not isolated to DVD's.
The salient point is DVD's (with the exception of BluRay) are appropriate for small data backups whereas external hard drives are more convenient for large backups. I wouldn't stake any claims on longevity to either forms of media which is why I am constantly testing my hard drives when I update the data and replace my drives every few years.
While what you say does have some truth, I have had HD's fail less than a week into using them and I know many other people that have had similar occurrences. HD's dont just fail after years and years of use. The problems with HD's is that any one of a hundred things can go wrong, and the bottom line is you NEVER know when that is going to be. When you buy that HD in the store you have absolutely no way of knowing whether that drive will last a week or 10 years. That just isnt the case with DVD's or any other high quality optical storage disc for that matter.
As for the rest of your post, convenience doesn't even play into it for me. I am making back ups of my life's work so if it takes a little work, or a lot of work for that matter, then so be it. I am not concerned about such things. As for how long DVD's have been around, I really have no clue what that has to do with anything. If your trying to suggest that we have no clue how long DVD's will last then I am not buying that for a second. Science and technology in general is not some big guessing game. We are not utterly clueless when it comes to understanding the long term storage capability of digital media. If that were the case then things would be very very different and you wouldn't see places like the Library of Congress using such technology. We may not know yet the maximum length of time that such media will remain functional however we do have a very good understanding of the minimum time they will remain useful and most of the high quality discs available claim at least 30 years with some claiming up to 100 years. Considering I already have burns that are 12-13 years old that are scanning as good as the day they were burned, without even a sign of old age, well I for one absolutely believe those figures and there is no data out there that proves otherwise.
As for those advantages, yes they absolutely are just for DVD's. If you can make an argument that disproves one of them, or all of them for that matter, then lets hear it.
I will openly admit if you back up on DVD's like a schmuck then your going to get burned however if you take the proper steps and use the proper media and storage supplies then backing up on DVD's is without a single doubt one of the safest and ultimately one of the best back up methods that exists today. I can tell you this in regards to backing up on redundant HD's, if you plan on shooting a lot and plan on practicing photography for the better part of your life then your going to reach a point, just as I did and just as every other photographer that I know did, where the cost in maintaining such back up systems becomes way way too expensive. Its simply not a good system for large collections, that is unless you have tens of thousands of dollars that you would rather spend on HD's than other things like new photo equipment. I for one would much rather dump that money into other things like new photography equipment, my sons education fund, etc...
Again to back up all of my pictures in such a method would easily cost well over 50,000 and that would just continue to increase substantially from year to year. The 10,000 DVD's I have burned on the other hand have cost me I would estimate around 3000-3500 with the storage cases and materials costing another 1500-2000. So it has basically cost me 4500-5500 dollars or around 450-550 dollars a year. Much better than the 50,000 or 5000 a year I would be spending on HQ Hard drives. Actually HD's have come way down in price. It would probably cost me 50,000 today to use that method but if I were to have used that method during the last 10 years it would have easily cost 2-3 times that much as HD's were vastly more expensive even just a couple years ago.
