Self hosting principals aside, is this data actually important? If so, then don't fuck around with self hosting it. Are you looking for lowest cost? Then don't waste a bunch of money spinning your own disks.
Amazon glacier to guarantee availability and your own encryption to guarantee privacy.
It's currently running me about $4/month for around 10tb that I don't want to lose but just don't want to deal with. An equivalent HDD solution would be around $500, that's 10 years to break even assuming zero disk failures and zero personal maintenance time.
Plus it's guaranteed. Inherent multiple copies, has SLA, and there's no worry about the service just disappearing. It's they decide to shut down or raise prices or whatever, you can reevaluate and move.
Edit: Glacier and similar services are meant for archival which is the term OP used. You never expect to need it again, but can't get rid of it. Retrieval cost is mostly irrelevant, but yes much more expensive.
(I'd wager still less expensive than a home RAID array.)
What would it cost to retrieve though? You probably still have the appropriate cost-effective solution but it's an important consideration for newcomers to have complete math.
Retrieving from S3 glacier is approximately 10 times the monthly cost of storing the data 100 times actually. Didn't realize retrieval from Glacier isn't actually downloading it onto your local, but rather just moving it into a frequent access tier S3 bucket from which you can then download, and this download is the expensive part.
So instead of "fucking around" with putting it on a long lasting storage device to keep in a wardrobe, he should give up control of the data, hand it to a company and risk forgetting to inform them about an adress change, so everything is lost, when the bills arent paid?
Guess it depends on how much you trust that Amazon is going to steal your data instead of doing the thing you're paying them for, vs a house fire or media failure or whatever.
There's also pretty clear rules about unpaid bills, the data doesn't just vaporize.
This is what we call a "risk assessment", and imo if I must have that data available long-term, then a single copy on DVDs in a closet isn't good enough.
I'd argue for most consumer use cases having one or better two physical back ups is more reliable, because it is simple and straightforward. Also the risk mitigation is already in place, as you wouldn't want your place to burn down either way.
/shrug
Do what works. I spent years maintaining disks in my basement full of data I never touched. Every now and any then I'd have to swap a disk for a couple hundred bucks. Twice, the entire Synology array failed and cost me 5-700. Now I pay $4-5/month and don't have to think about it ever again otherwise.
Is it Glacier Deep Archive? I just realized I was looking at the Glacier flexible retrieval prices earlier. US-East lists it as $0.00099/GB (about $1/TB), which is still higher than what you're getting.
Still less than an equivalent RAID array. Particularly if you consider that archives are very rarely extracted as a complete bulk, vs pulling the specific records needed.