Please don't rely on only one cloud service like Dropbox. If not already, keep 1 more copy backed up locally.
Uggh, it's expensive to meet that duplicate backup requirement (and I agree with it!)
What are your thoughts on a single backup say with S3/B2/Impossible, etc? 25TB is quite a bit to have a local backup plus online (though it's the right answer).
Yeah, a giant home NAS that automatically uploads things to S3 with a lifecycle rule to automatically move rarely used files to S3 Glacier.
I'd look into cloud-based backup (for the off-site component) using something like Backblaze B2 to ensure you don't lose the data on that external drive when it fails.
IIRC, 25gb on B2 is about $30/mo. ImpossibleCloud is about the same.
From a get-files-to-home while remote standpoint, Syncthing is hard to beat. It works, it has clients for every OS, it's encrypted, it's free.
I'd probably also look for more robust storage at home. External drives are notorious for failures. In 30+ years of doing this stuff, I've had a handful of internal drives fail (perhaps 3%, at most). While externals it's more like 15%, and that's in a relatively short time, within 2 years of use. Externals get dropped, experience greater and more frequent temp cycles, and lack cooling.
I haven't priced consumer NAS lately, but for 25+ TB, that's where I'd be looking. And that would also potentially give you an OS that can run things like Duplicati and Syncthing.
Photophrism
A place to share alternatives to popular online services that can be self-hosted without giving up privacy or locking you into a service you don't control.
For Example
We welcome posts that include suggestions for good self-hosted alternatives to popular online services, how they are better, or how they give back control of your data. Also include hints and tips for less technical readers.
Useful Lists