Selfhosted

I'm using blu-ray disks for the 3rd copy, but I'm not backing up nearly as much data as you are.

The only problem with optical media is that you should only expect it to be readable for a couple of years, best case, at this point and probably not even that as the tier 1 guys all stop making it and you're left with the dregs.

You almost certainly want some sort of tape option, assuming you want long retention periods and are only likely to add incremental changes to a large dataset.

Edit: I know there's longer-life archival optical media, but for what that costs, uh, you want tape if at all possible.

I have not used them myself, but M-DISC sounds like what you’re looking for. There are a few other alternatives listed on that Wikipedia article, too.

I usually use a dehydrator for ~3 days on my drives to make them shelf stable. So far I haven’t had any issues.

Tape. Amazon glacier if you're okay with that.

And regular test restores. An untested backup is not a backup.

But when considering what I need to back up, I usually overestimate how much I or other people will care if it's lost. Family photos are great, but what are the odds of someone saying "damn I wish we still had two dozen photos of that one barbecue?"

Currently the only solution for a consumer are M-Disc Blue rays. They are currently the only "write once read many" media available that are preferable in these types of situations.

The media is comparable cheap - you can safe your amount of data for around 80-90USD/€ initially(or less for more but smaller discs) and then pay around 10$/€ per year for the new amount of data.

The chances that in 20 years someone is still able to read them are fairly high - there are numerous businesses that are using these disc as WORM media to backup important data on a medium that a opposing lawyer later cannot claim "was manipulated". In 50 years it is very likely to be readable at least by professionals. The discs itself are rated for much longer storage.

If you write on them unencrypted there should be no problem of writing on them. Additionally they do not have issues with byte rot,etc.

The other thing is if I get hit by a bus and no one can work out how to decrypt a backup or whatever.

Documentation, documentation, documentation. No matter what system you have, make sure your loved ones have a detailed, image-heavy, easy to follow guide on how restorations work - at the file level, at the VM level, at whatever level you are using.

That being said, DVDs actually have quite a short shelf life, all things considered. I'd be more inclined to use a pair of archival strength USB NVME drive, updated and tested routinely(quarterly, yearly, whatever makes sense). Or even an LTO tape, if you want to purchase the drive and some tapes.

You can put your backups in something like VeraCrypt. Set an insanely long password, encoded in a QR code, printed on paper. Store it in the same secured location you store your USB drives (or elsewhere, if you have a security posture).

You may also consider, if money is not a concern, a cloud VPS or other online file storage, similarly encrypted. This can provide an easy URL to access for the less tech-savvy, along with secured credentials for recovery efforts. Depending on what your successors might need to access, this could be a very straightforward way to log into a website and download what they need in an emergency.

This was a recent point of discussion on the 2.5 Admins podcast (https://2.5admins.com/2-5-admins-228/). Some good discussion on there.

My own thought is the best way to handle your family-member-finding-your-old-photos problem is the analog way: make some prints. It’s absolutely idiot proof, the methodology of keeping paper goods is well understood, and the technology is platform independent.

After reading the previous discussion I think that you should get more than single drive to store cold backups. That way you can at least spread out the risk of single drive failing. 2TB spinning drives are pretty cheap today and if you have, for example, 4 of them, you can buy one now, write your backups to it and in 6 months buy another, write data on that and so on.

This way you'll have drives with year or two difference on purchase date, so it's pretty unlikely all of them fail at once and a single drive gets powered on and checked every other year or so. My personal experience is that spinning drives are pretty stable on the shelf, but I wouldn't rely on them for decades. And of course even with multiple drives you'll still want to replace them every 3-5 years each. Plus with multiple drives, if I were to build setup like that, I'd set up some sort of scripts or other solution where I can just plug the thing in and doubleclick an icon on desktop to refresh the data and maybe get a notification automatically that the drive you're using should be replaced.

And for actual, long term storage, printouts are the way to go. At least in here you can get books made out of photo paper with your pictures. That's one media which is actually stable over long period and using them doesn't require a lot of technical knowledge nor hardware. But I'd still keep digital copies around, as the printouts aren't resistant to things like house fire or water damage.

For your amount, just an external hard drive attached to a NAS or something is fine, or a 2-bay synology would be more than enough. Drives are coming in 20-24TB models now, that'd keep you going for a long time.

USB hard drive? If we're talking about a cold backup that's easy to access a USB drive is reliable and easy.

In your scenario, I'd be looking at ZFS or BTRFS for your live data, especially when taking photos into account. They'll self-repair files that may run into decay issues, which I've seen a lot of with photos in all formats. Since you already keep off-site backups, I'd then just keep an extra drive around that you snapshot to from time to time.

I believe M-Disc to be the best consumer grade, optical solution out there. If you want to go commercial grade you are looking for LTO tapes, but your costs begin rising exponentially. If M-Disc claims are to be believed, they should last well longer than your requirement and be able to handle your data footprint using multiple, but not an unreasonable amount of discs.

No matter which solution you choose, if you are targeting multiple decades, you must save not only the media, but ideally the drive, computer and software used to archive. There is no guarantee that any of the existing technology will be relevant or backward compatible across several decades.

Just a hdd in usb caddy? IMHO good enough for 4 tier backup.

This is why I do my first-level of backups with rsnapshot. It backs up to the plain filesystem using rsync and uses hard-links to de-dup between backups. No special filesystem, no encryption, restore is just an 'rsync' away.

For photos? Archival prints. As a bonus, you also get a cool album to reminisce later in life.

For local backups it depends on what you want to have:

• The cheapest option is a usb or thumb drive. But you have to regularly plug it in and copy your backup on it.
• The lazy option is to buy a NAS and configure a backup job that regularly creates a backup. Versioned, incremental, differentials and full backups are possible as is WORM to add a bit of extra security. You can configure a NAS to only turn on specified times, do a backup and then turn off again. This will increase protection against encrypting malware. WORM also helps in this case.
  Or just let it run 24/7, create backups every hour and install extra services on it like AI powered image analysis to identify people and objects and let it automatically tag your photos. Cool stuff! Check out QNAP and Synology or build a NAS yourself.
  A NAS can also be configured to present its content in a LAN by itself. Any computer will automatically connect to it if the access isn't secured by user/password or certificate.

I recommend buying a NAS.

ZFS with automatic snapshots and scrubbing. This will keep as many and as old snapshots as your like. It'll ensure the files don't rot. It'll ensure the media doesn't die, so long as you have enough redundancy and you replace disks as they die. This is what I'd trust for long term storage because I think I understand how and why it works. It should last as long as I feed it disks. If I delete something, I should be able to restore it from a snapshot. The hardware doesn't need to be anything fancy. Just a Pi 4/5 with a couple of WD Elements would be fine. Could add more disks for more redudnancy. I'm running 2-disk residency.

You don't have to touch the software if it's not exposed to the Internet. Whatever works today on it will work 20 years from now, so long as the hardware works. A couple of spare Pis, SD cards and power supplies should let it last for decades.

I decided instead to use ZFS. Better protection than just letting something sit there. Your backups are only as good as your restores. So, if you are not testing your restores, those backups may be useless anyway.

ZFS with snapshots, replicated to another ZFS box. The replicated data also stores the snapshots and they are read-only. I have snapshots running every hour.

I have full confidence that my data is safe and recoverable.

With that said, you could always use M-disk.

I'm thinking of using a HDD and keeping it at work, which is climate controlled. I'd bring it back every few months to sync the latest.

Since it's constantly being used, I'm pretty confident it'll be usable as a backup if my NAS fails, so it only needs to be "shelf stable" for a few months at a time. If you're retired or something, a safe deposit box at your local bank should do the trick.