Hi,

Since LVM and virtual machines are part of the mix, you might find Wyng interesting. It backs up thin-provisioned LVs much the way btrfs-send and zfs-send do for their filesystems, using metadata for incremental backups so it doesn't have to compare (or hash) files byte-by-byte; it can find changes immediately. This is usually more efficient than traditional backup tools that ignore copy-on-write storage features. However, a matching storage format is not required for the backup archive... it only requires a Unix filesystem for back end storage.

I wrote a Wyng HowTo for Ubuntu here:
https://ubuntuforums.org/showthread.php?t=2437700