[linsomniac]

>back up multiple hosts to the same repository

I haven't tried that recently (~3 years), does that work with concurrency or do you need to ensure one backup is running at a time? Back when I tried it I got the sense that it wasn't really meant to have many machines accessing the repo at once, and decided it was probably worth wasting space but having potentially more robust backups. Especially for my home use case where I only have a couple machines I'm backing up. But it'd be pretty cool if I could replace my main backup servers (using rsync --inplace and zfs snapshots) with restic and get deduplication.

[sureglymop]

It works. In general, multiple clients can back up to/restore from the same repository at the same time and do writes/reads in parallel. However, restic does have a concept of exclusive and non-exclusive locks and I would recommend reading the manual/reference section on locks. It has some smart logic to detect and clean up stale locks by itself.

Locks are created e.g. when you want to forget/prune data or when doing a check. The way I handle this is that I use systemd timers for my backup jobs. Before I do e.g. a check command I use an ansible ad-hoc command to pause the systemd units on all hosts and then wait until their operations are done. After doing my modifications to the repos I enable the units again.

Another tip is that you can create individual keys for your hosts for the same repository. Each host gets its own key so that host compromise only leads to that key being compromised which can then be revoked after the breach. And as I said I use rest-servers in append-only mode so a hacker can only "waste storage" in case of a breach. And I also back up to multiple different locations (sequentially) so if a backup location is compromised I could recover from that.

I don't back up the full hosts, mainly application data. I use tags to tag by application, backup type, etc. One pain point is, as I mentioned, that the snapshot IDs in the different repositories/locations are different. Also, because I back up sequentially, data may have already changed between writing to the different locations. But this is still better than syncing them with another tool as that would be bad in case one of the backup locations was compromised. The tag combinations help me deal with this issue.

Restic really is an insanely powerful tool and can do almost everything other backup tools can!

The only major downside to me is that it is not available in library form to be used in a Go program. But that may change in the future.

Also, what would be even cooler for the multiple backup locations, is if the encrypted data could be distributed using e.g. something like shamir secret sharing where you'd need access to k of n backup locations to recreate the secret data. That would also mean that you wouldn't have to trust whatever provider you use to back up to (e.g. if it's amazon s3 or something).

[l33tman]

The issue with this is that if someone hacks one of the hosts now they have access to the backups of all your other hosts. With borg at least and the standard setup, would be cool if I was wrong though

[sureglymop]

At least with restic that is not an issue. See my other comment here: https://news.ycombinator.com/item?id=44626515

Backups are append only and each host gets its own key, the keys can be individually revoked.

Edit: I have to correct myself. After further research, it seems that append-only != write-only. Thus you are correct in that a single host could possibly access/read data backed up by another host. I suppose it depends on use-case whether that is a problem.

[linsomniac]

It would be nice if one of the backup systems supported public key crypto for the bulk of the data, so that the keys used for recovering data would be different from the keys used for backing up. I know there is an open ticket for one of restic/borg, because I subscribed to it a few years ago and periodically get updates on it, but nobody has come up with a solution to it yet.