Wyng-backup: Fast Time Machine-like backups for logical volumes
github.com
github.com
You should rewrite this with libdevmapper instead of shelling out to 10's of shell tools. It will likely be both more robust, faster and result in cleaner logic.
Otherwise the idea looks great. I would also consider adding native cloud storage option, ala S3 and friends as that would make it the most useful.
Careful! Egress bandwidth is insanely expensive for almost all cloud providers. GCP is $0.12/GB, so downloading a 1TB backup would cost you $120.
You can get a 64TB Hetzner server for 79 euros a month + free bandwidth: https://www.hetzner.com/dedicated-rootserver/matrix-sx
So, please keep it as is, continue to do this one thing well, and leave cloud synchronization to the number of other tools already exist to this end.
I wonder if it is useful to consider the duties of backup (which may include version) and synchronization as separate. At least it helps me not fall for the false security in thinking that one system will just do everything.
One interesting thing I did at one point was to clone and mount LVs of running Windows VMs, so I could then rsync backup them on the same backup server. With the exception of a handful of physical boxes, my fleet is entirely Linux VMs running on Ganeti hosts with LVM for storage.
This project has me imagining doing VM-level backups by talking to the ganeti hosts and backing up LVM clones outside the host, rather than rsyncing into the host.