I believe M-Disc to be the best consumer grade, optical solution out there. If you want to go commercial grade you are looking for LTO tapes, but your costs begin rising exponentially. If M-Disc claims are to be believed, they should last well longer than your requirement and be able to handle your data footprint using multiple, but not an unreasonable amount of discs.
No matter which solution you choose, if you are targeting multiple decades, you must save not only the media, but ideally the drive, computer and software used to archive. There is no guarantee that any of the existing technology will be relevant or backward compatible across several decades.
I believe M-Disc to be the best consumer grade, optical solution out there. If you want to go commercial grade you are looking for LTO tapes, but your costs begin rising exponentially. If M-Disc claims are to be believed, they should last well longer than your requirement and be able to handle your data footprint using multiple, but not an unreasonable amount of discs.
No matter which solution you choose, if you are targeting multiple decades, you must save not only the media, but ideally the drive, computer and software used to archive. There is no guarantee that any of the existing technology will be relevant or backward compatible across several decades.