I've looked into Borg/Attic as well. My main hang-up is where to put the repository and what my long-term storage costs would be. Right now I have somewhere in the neighborhood of a terabyte of stuff backed up (mostly my Lightroom catalog). I need to be able to generate and access these backups from anywhere in the works reliably.
I think Borg would be a great solution for my use at home where I have a NAS on my LAN to provide local storage for the repository. But while traveling the world with my MacBook it doesn't cut it.
Arq looks good from that angle but I think would quickly cause my costs to overrun me. Having good backups is what gives me the confidence as a photographer to overcome my inner pack rat. Without good backups I'd never be able to ruthlessly delete images from my collection that don't exceed "okay" into "great". But because I know my images are backed up effectively forever I can really be honest in my art.
Arq can write to Amazon Cloud Drive, which has unlimited storage for $5/mo.
I personally use Arq against Google Cloud Storage. I have around 1TB, and I use it to back up several external drives in addition to my MacBook. (Arq is nice in that it backs up the drive if it's connected, but won't prune olds backups if it's not, unlike services such as Backblaze.)
I think I pay around $6-7/mo. I use a coldline bucket, which is the cheapest kind of bucket. Restoring is super fast (unlike Amazon Glacier, which I used previously) and not too expensive.
Correction: "Unlimited" storage. Chances are high that you'll find yourself getting nasty emails (or worse) if you actually try to put a significant quantity of data up there.
I wouldn't risk my amazon account on it, personally.
Amazon does aggressively monitor and shut down accounts that store pirated content, but I've yet to hear any reports of Amazon cracking down on the amount of storage used.
There are plenty of people who are storing absurd amounts of data [1]. If Amazon were cracking down on this, you'd hear it in /r/DataHoarder first.
The ToS [2] don't mention any size limitations. In fact, it says you can store pretty much any file as long as the data doesn't violate any laws, including copyright.
The only really worrying part is this:
3.2 Usage Restrictions and Limits. The Services are offered
in the United States. We may restrict access from
other locations. There may be limits on the types of
content you can store and share using the Services,
such as file types we do not support, and on the
number or type of devices you can use to access the
Services. We may impose other restrictions on use
of the Services.
I use Arq too, however, there are some limitations:
- Scanning of new / changed files takes could be faster and less demanding for the file system (on my Macs, Finder sometimes temporarily freezes when Arq is scanning for new / changed files)
- Mail reports for '0 errors' (all the time, so the mail reports for errors only are rather useless)
- Running in user context only, i.e., if you log out while your Mac is still running, the backup will not continue
- Loading of existing backups (reading / caching index) tends to be slow (and sometimes hangs)
- GUI does not scale up for many existing backups
With that being sad, you listed the major reasons to use Arq and all in all, I am a happy Arq user.
https://www.arqbackup.com