This is my day job, so I’d like to weigh in.

First of all, there’s a whole community of GLAM institutions involved in what is called Digital Preservation (try googling that specifically). Here in Germany, a lot of them have founded the Nestor Group (www.langzeitarchivierung.de) to further the case and share knowledge. Recently, Nestor had a discussion group on Personal Digital Archiving, addressing just your use case. They have set up a website at https://meindigitalesarchiv.de/ with the results. Nestor publishes mostly in German, but online translators are a thing, so I think you will be fine.

Some things that I want to address from your original post:

• Keep in mind that file formats, just like hardware and software, become obsolete over time. Think about a migration strategy for your files to a more recent format of your current format falls out of style and isn’t as widely supported anymore. I assume your photos are JPGs, which are widely not considered safe for preservation, as they decay with subsequent encoding runs and use lossy compression. A suitable replacement might be PNG, though I wouldn’t go ahead and convert my JPGs right away. For born digital photo material, uncompressed TIFF is the preferred format.
• Compression in general is considered a risk, because a damaged bit will potentially impact a larger block of compressed data. Saving a few bytes on your storage isn’t worth listing your precious memories.
• Storage media have different retention times. It’s true that magnetic tape storage has the best chances for survival, and it’s what we use for long term cold storage, but it’s prohibitively expensive for home use. Also, it’s VERY slow on random access, because tape has to be rewound to the specific location of your file before reading. If you insist on using it, format your tapes using LTFS to eliminate the need for a storage management system like IBM Spectrum Protect. The next best choice of storage media are NAS grade HDDs, which will last you upwards of five years. Using redundancy and a self correcting file system like ZFS (compression & dedup OFF!) will increase your chances of survival. Keep you hands off optical storage media; they tend to decay after a year already according top studies on the subject. Flash storage isn’t much greater either, avoid thumb drives at all cost. Quality SSD storage might last you a little longer. If you use ZFS or a comparable file system that provides snapshots, you can use that to implement immutability.
• Kudos for using Linux standard tooling; it will help other people understand your stack of anything happens to you. Digital Preservation is all about removing dependencies on specific formats, technologies and (importantly) people.
• Backup is not Digital Preservation, though I will admit that these two tend get mixed into one another in personal contexts. Backups save the state of a system at a specific point in time, DigiPres tries to preserve only data that isn’t specific to a system and tends to change very little. Also, and that is important, DigiPres tries to save context along with the actual payload, so you might want to at least save some metadata along with your photos and store them all in a structure that is made for preservation. I recommend BagIt; there’s a lot of existing tooling for creating it, it’s self-contained, secured by strong checksums and it’s an RFC.
• Keep complexity as low as possible!
• Last of all, good on you for doing SOMETHING. You don’t have to be perfect to improve your posture, and you’re on the right track, asking the right questions. Keep on going, you’re doing great.

Come back at me if you have any further questions.

Wherever you choose to store it, you should still consider following the 3-2-1 backup rule.

Don’t use DVDs or other disc media

https://en.m.wikipedia.org/wiki/Disc_rot

Assume anything you can buy has a shelf life and set a yearly reminder on your calendar to copy forward stuff more than five or so years old, if those files are of significant value to you. Or for the documents, print them out—paper has better longevity than any consumer-available electronic storage.

That being said, quality optical discs are probably the best option in terms of price to longevity ratio for the average person right now. Just keep in mind that they are not guaranteed to last forever and do need to be recopied from time to time.

(I have yet to have a DVD fail on me, but I keep them in hard plastic jewel cases in climate-controlled conditions, and I’ve probably just been lucky.)

The local-plus-remote strategy is fine for any real-world scenario. Make sure that at least one of the replicas is a one-way backup (i.e., no possibility of mirroring a deletion). That way you can increment it with zero risk.

And now for some philosophy. Your files are important, sure, but ask yourself how many times you have actually looked at them in the last year or decade. There’s a good chance it’s zero. Everything in the world will disappear and be forgotten, including your files and indeed you. If the worst happens and you lose it all, you will likely get over it just fine and move on. Personally, this rather obvious realization has helped me to stress less about backup strategy.

NAS

I am using https://duplicati.com/ and https://www.backblaze.com/ ( use their b2 cloud storage its variable and 6$ a month for 1TB or less depending on how much you use) run a schedule beckup every night for my photos. It’s compressed and encrypted. I save a config file to my google so say if my house and server burn down. I just pull my config from google then redownload duplicati and boom pull my back up down. The whole set up backs up incremental so once you do the first back up its only changes that are uploaded. I love the whole set up.

Edit: You can also just pull files you need not the whole backup.

I used to write to DVD’s, but the failure rate was astronomical - like 50% after 5 years, some with physical separation of the silvering. Plus today they’re so relatively small they’re not worth using.

I’ve gone through many iterations and currently my home setup is this:

• I have several systems that make daily backups from various computers and save them onto a hard drive inside one of my servers.
• That server has an external hard drive attached to it controlled by a wifi plug controlled by home assistant.
• Once a month, a scheduled task wakes up that external hdd and copies the contents of the online backup directory onto it. It then turns it off again and emails me “Oi, minion. Backups complete, swap them out”. That takes five minutes.
• Then I take the usb disk and put it in my safe, removing the oldest of 3 (the classic, grandfather, father, son rotation) from there and putting that back on the server for next time.
• Once a year, I turn the oldest HDD into an “Annual backup”, replacing it with a new one. That stops the disks expiring from old age at the same time, and annual backups aren’t usually that valuable.

Having the hdd’s in the safe means that total failure/ransomware takes, at most, a month’s worth. I can survive that. The safe is also fireproof and in another building to the server.

This sort of thing doesn’t need to be high capacity HDDs either - USB drives and micro-SD cards are very capable now. If you’re limited on physical space and don’t mind slower write times (which when automating is generally ok), the microSd’s and clear labelling is just as good. You’re not going to kill them through excessive writes for decades.

I also have a bunch of other stuff that is not critical - media files, music. None of that is unique and can be replaced. All of that is backed to a secondary “live” directory on the same pc - mostly in case of my incompetence in deleting something I actually wanted. But none of that is essential - I think it’s important to be clear about what you “must save” and what is “nice to save”

The clear thing is to sit back and work out a system that is right for you. And it always, ALWAYS should be as automated as you can make it - humans are lazy sods and easily justify not doing stuff. Computers are great and remembering to do repetitive tasks, so use that.

Include checks to ensure the backed up data is both what you expected it to be, and recoverable - so include a calendar reminder to actually /read/ from a backup drive once or twice a year.

Don’t over complicate it. 3 copies: backup, main, and offsite; 2 different media: hdd and data center; 1 offsite. I like blackblaze but anything from google to Amazon will work.

There isn’t anything that meets your criteria.

Optical suffers from separation, hard drives break down, ssds lose their charge, tape is fantastic but has a high cost of entry.

There’s a lot of replies here, but if I were you I’d get last generation or two’s lto machine from some surplus auction and use that.

People hate being told to use magnetic tape, but it’s very reliable, long lived, pretty cost effective once you have a machine and surprisingly repairable.

What few replies are talking about is the storage conditions. If your archive can be relatively small and disconnected then you can easily meet some easy requirements for long term storage like temperature and humidity stability with a cardboard box, styrofoam cut to shape and desiccant packs (remember to rotate these!). An antifungal/antimicrobial agent on some level would be good too.

I use external hard drives. Two of them, and they get rsynced every time something changes, so there’s a copy if one drive should fail. Once a month, I encrypt the whole shebang with gpg and send it off into an AWS bucket.