At your scales, bluray discs are probably the most affordable per GiB year (looks like 2.5T spread out across 100x discs is about $80 right now and should last

At your scales, bluray discs are probably the most affordable per GiB year (looks like 2.5T spread out across 100x discs is about $80 right now and should last 15-25 years or more). Double or triple your data and you should just use cold hard drives. 10x or more and you should probably use magnetic tapes. Mirror everything 2-3x and do yearly integrity checks (I just write the SHA of my discs on the disc label) and your data should last a good long time.