Obviously the best medium to store the data is HDD, just because of the $/TB ratio. You can get high capacity drive for really cheap. Also, if there nothing special is required in terms of performance, I wouldn't look into SSDs.
Data Hoarder
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
Blu rays?
In terms of actual use and access, CMR is much better. Flash would be better yet. Higher capacity hard drives are the most economically efficient option.
Mind if recoverability is a priority you'll have to avoid Helium drives. Also backups >>>> recoverability.
A friend. Make your friend hoard data. And share it with you.
Otherwise large HDDs, at least 18TB, are most likely still the cheapest per TB. If you mostly write once and read much, much more, then SMR is fine. As long as it isn't in a RAID array that may have to be rebuilt.
SSD is, I think, better in all ways, except price and capacity. So SSDs are very bad for bulk storage.
Multiple backup copies on different media, stored at different locations, is how you reduce the risks of data loss.
I guess until I can afford that I'll Make copies with 2Tb dives. Would this be A good Idea?
It is a very good idea!
Any medium can fail, and if you need something and get it easily any other way you should have backups, not micromanaging which one fails more, CMR or SMR.
HOWEVER, when discussing cost effective and hoarding the best price/TB is by far for larger disks and larger disks aren't SMR, problem solved.
Is there a way to check? Like the 2 tb Barracuda, how would I know what technology it uses?