As I said, however, the HD is electronically and mechanically more complicated (and hence less robust) than just the physical media alone.
In the overall picture, I'm not sure which one is more reliable.
But I am. And more complicated does not imply less "robust". And no backup system is "just the physical media alone".
"Physical media alone" assumes you, the user, secures that physical media (many disks) and protects it for years to come from any physical damage, including a simple scratch to soft plastic surfaces. And it assumes you will have a working drive, with a different set of R/W heads, that supports it. Who knows what optical storage (or their readers) will look like in 10 years? I hope not big clunky, scratchable plastic disks. Sure, hard drives need to be stored too, but they can take some rough handling (compared to optical disks), and one HD can take the place of many scratchable disks. And the HD only needs an SATA interface to plug into - not a compatible reader. I suspect SATA will still be around.
But you still need to do what is best for you, and my opinion does not matter. If you can ensure the easily damaged burned disks are safely secured away for years to come, and you don't care about all the extra time and extra work needed to burn (and restore from) a whole bunch of disks, that's fine. And frankly, there's nothing wrong with having multiple copies in different formats to ensure recovery years down the road either.
Past problems come for incompatible implementation of standards support
And in hardware parlance, is the same thing as not adhering to specified tolerances.
My background is Elec Eng, but not in the design of disc drives. Does anyone know if the standards specify how tolerant the readers have to be to wandering tracks? Also, do the standards specify how accurate the track positions have to be for writers?
Well, I am not an EE but you can follow the link in my sig and decide if I might have any "practical experience" to qualify my comments. Those would be engineering/design/theory questions, but sure, Sony and Phillips dictate and own the standards for CDs; Sony, Phillips, Toshiba, and Panasonic for DVDs; and the
BluRay Disc Association for BluRays.
But theory and real-world rarely see eye-to-eye - especially on budget models. And until Man can create perfection 100% of the time, there will always be a few samples a few nanometers too far off to the right, and few samples a few nanometers too far off to the left.
Put the two samples together and potentially, perfect alignment is off by way more than few nanometers. The higher the density, the more bits of data is stored per square millimeter and the tighter the tolerances must be. But it is still up the manufacturer of the end product ensure that, and clearly, they have an interest to ensure they do.
Fortunately, they are pretty good at it.
From your response, I guess that your answer to my question is that you simply assess these factors differently for your needs, and the HD comes out on top.
No, you are discarding many factors I don't. Such as,
Costs per Gb
Time (much faster backing up to one HD than burning to several optical disks)
"Durability" - HDs are much more robust.
Flexibility - you can erase and write over data with an HD
Space/Storage - one HD is easier to safely store for years than a bunch of soft plastic disks
Ease of use - backing up and restoring from one HD is relatively ease
