Before someone points it out, the individual drives in the array have build dates that differ by at least a year.
In addition; for really critical stuff only (accounting data, deeds, business contracts, access codes, software source code, etc.) I use micro SD cards for more frequent backups as needed.
I have a cheap digital watch with a SD card holder that I 3D printed and built into the strap. The SD drive is encrypted with Bitlocker and it travels with me wherever I go.
Basically, this really critical data is as safe as I am. I always make 2 copies of the SD drive and keep one in a fire proof safe. The key to the safe is revealed in my will which my lawyer has. Inside the safe is the decryt key to the SD card. A trusted relative also has the decrypt key.
It runs inside a Docker container and backs up both my data as well as configurations like my docker compose file and smb.conf.
Off site storage was Backblaze B2, but I moved to Hetzner. Likely will move back just because B2 is cheaper and a bit faster for my region.
Another layer of backup I do is use Duplicacy to backup to a portable hard drive occasionally that I keep off site.
Technology-wise, I've been on restic for some years now, because of its support for cloud backends. (Otherwise, Borg is a fine tool, too.) Until last week, I've used crestic, but I just migrated to resticprofile, as that can do web hooks and pre-/post-commands, which I intend to use for SQL server dumps.
restic: https://github.com/restic/restic/ crestic: https://github.com/nils-werner/crestic resticprofile: https://github.com/creativeprojects/resticprofile/
This reduces my backup set from tens of terabytes to less than one terabyte. And makes it easier to keep many more copies of the very special things (photographs, documents) on multiple devices and cloud services.
Those backups are also pushed to an offsite location (with a hosting provider).
Laptop and NAS run on a single disk rootfs, Desktop and Server run on mirrored nvme drives.
I have another small machine (a nuc) with a similar setup at in law’s house, connected to my vpn, and I replicate snapshots over there through the vpn.
Worst case scenario i can go visit the in law’s and get my snapshots.
Zfs is really awesome.
Edit: everything is scripted and ran via cronjobs, of course.
[0] https://www.borgbackup.org/ [1] https://torsion.org/borgmatic/
I loaded up $10 credit like 6 years ago and it's still going somehow
I got one on FB marketplace for cheap, i think I will put a faster spinning drive in there and should be good until apple kills support.
Edit: to be clearer it’s something I wrote myself from scratch.
It is synchronized with Google Drive.
So I can access my files with the peace in mind there is a back up.