Thanks. I have spent the day reading about M-disc and optical formats. Lemmy is great for starting rabbit holes! I think I may swap a blu-ray burner into one of my machines and I am actually thinking dual layer blu ray is a decent trade-off: simmiliar chemistry to m-disc (unlike the clear superiority of m disc over DVDs -which I was literally burned on the other week with some yellowed DVDs), and yet still cheap, reasonable amount of disc shuffling, and in the future, nearly any blu ray drive will work with the 50gb discs (unlike 100gb disks). Still might grab a blu ray m disc burner if I see a good deal but they seem rarer than a hens tooth. Lol.

I have less than a TB of truly irreplacable stuff, so 20 discs isnt bad to suffle, and aiming for maybe 20 years of electrically safe cold storage* zero maintenance off-site seems pretty reasonable for a $50 drive and about that in discs.

*This is overkill anyway - already have zfs snapshots going to an external drive in another room and restic backups to b2. But the threat model is some combination of losing b2 (credit card fail or my own incompetence) plus housefire/robbery/electrical surge taking out everything. Also, if I get hit by a bus and my CC is cancelled, a box of transparrently readable discs are significantly safer bet for my survivors than my note about how to get the data off the NAS/backup drive. They could leave it 5+ years and come back to it no problem.

I have wondered about how to manage a 100 spool of DVDs as long term cold storage of the most important data. Would need some way of splitting the data up automatically and building a straightforward burning workflow, with redundancy incase a disk is destroyed, and a way to find a given file.

Seems like a lot of work for 400-ish Gb, but 1. Its very cheap, 2. Archival disks could last a lot longer in cold storage than anything else affordable, and 3. Anyone could recover it in the future because DVD drives have been manufactured by the billion and are still being put in some office PCs. 100gb blurays are also an option but that means sourcing a burner and at least a few drives capable of reading them to store alongside.

Edit: at first blush, plain files to make recouvery easier plus par2 files scattered across enough disks to be able to lose a whole disk or have many damaged disks seems like the right format. Some sort of index would need to be built and left on every/most disks or maybe printed on paper. Its mainly the workflow to do it that would be a PITA. Then maybe vacuum seal the spool with some moisture and oxygen absorbers and put in a lightproof container. Good for decades later? Maybe.

I just restored from some 20 year old dvds and they had visible yellowing at the edges and lost data at the end. A few videos were unrecouverable, not many.

Use a gell cell lead acid battery (the kind that go in regular UPSs). No fire hazzard, ans bonus, they can survive freezing temperatures just fine if outdoors. Downside is replacing a cheap battery every 3 years.

Security by obscurity is when the design or archetecture of the system is obscure enough to supposedly styme attackers (it doesnt), and as soon as people understand the design, your security is broken.

A hard to guess unpublished subdomain is a transparent and standard archetecture - nothing obscure about it and publishing that you use such a scheme doesnt break the security.

The subdomain is a bearer token that serves as an access control and just like a key or passphrase, has a security value proportional to the bits of information an attacker has to guess.

The real limitation is that browsers and humans are not great at not leaking domain names, so its very possible it will get leaked eventually and hard to rotate. Thats the reason they are weak. Still, they can be usefull to stop scanners just trolling for unpatched services.