There's no single right answer, and a lot of the value of a place like this is seeing what people actually do in practice — one external drive, a NAS, cloud, M-Disc, or some mix. If you want the principles behind it (the "a single copy isn't an archive" stuff, and which file formats age well), I've written those up across the family-archive series: Part I — Backups and Part II — Preservation.

But mostly I'd like to hear your real-world setup. So — how are you storing your collection right now, and what worries you about it? Post what you've got, even if it's "one drive and a prayer", and we'll help you spot the gaps. No question's too basic here.