Feature proposal: switching to restic for backups?

[duxovni]

I'm curious whether people would be open to switching MIAB's backup utility from duplicity to restic. Advantages I see are:

• Speed: restic is substantially faster than duplicity, meaning less downtime while services are stopped to avoid backing up files in a corrupted/inconsistent state. In addition, restic won't need to periodically make full backups that take way longer and introduce way more downtime than usual; its backups are always deduplicated, within the current backup and between previous backups.
• Efficient integrity checking: restic allows checking the integrity and consistency of backups, to guard against bitrot and against malicious modifications to some degree. It allows quick checks that only verify the structure of the backup repository, more time-consuming checks that verify integrity of all of the backed-up data, and a middle ground that verifies a configurable fraction of the data each time, saving time while also eventually detecting any data corruption. These checks can be run separately from creating the backups, so they don't need to contribute to downtime at all.

It supports all the same backends MIAB currently accepts, so it shouldn't necessitate any big changes aside from deleting the old duplicity backups at some point. The main disadvantage is that it doesn't support compression; it tries to perform deduplication in a way that makes watermarking attacks more difficult, and compression would require even more careful thought to mitigate such attacks. So viewed naively, restic backups would take up more space than duplicity backups, although once there are multiple full duplicity backups present, the story may be different.

The long downtime during full backups is my biggest pain point with MIAB, and I think this would improve things substantially. Thoughts?

[nomandera]

I hear a lot of buzz about restic and probably more importantly people putting the effort into moving to it.

In the context of mailinabox though. Does it need to maintain a local copy of the backup? This would regression for some but a show stopper for many. For example I have a VPS which is plenty large enough for my needs but would not have enough space to support a second uncompressed copy of mailboxes.

[duxovni]

AIUI it doesn't need a second local copy of anything, it just looks at the source files directly. Although having a backup destination on the local disk, and then copying that backup repository elsewhere separately, is also a supported option if desired.