M-Disk is a somewhat pricey but apparently legit archival format that appeared (from my point of view) just as the DVD/Blu-ray external writers market collapsed.
I now have an external HDD in a portable fire-safe that I know could go from 100% working to 0% working at any moment. The thing I liked about optical is you could have some hope of recovering most data as the media degraded, and basically all with judicious use of ECC. It's a shame.
Those safes are prone to mold. Not a good place to store backup mechanical equipment unless you compensate by opening it often and re/placing dessicant packets.
I now have an external HDD in a portable fire-safe that I know could go from 100% working to 0% working at any moment. The thing I liked about optical is you could have some hope of recovering most data as the media degraded, and basically all with judicious use of ECC. It's a shame.