Summary:

• Creating snapshots on btrfs is not recursive, the snapshot stops at nested subvolumes.
• Create additional subvolumes in order to exclude (or treat with special handling) certain locations from a snapshot, send and receive, and restore regime.
• Subvolumes are dedicated btrees, with their own fd (file descriptor) and inode pool.

Detailed explanation:

• Creating subvolumes in nested form

  • Dilemma: A rollback will need to move these subvolumes to a new location, because they're nested in the old/abandoned subvolume.

• Create subvolumes at the top-level, add them to fstab or native systemd mount.

  • Dilemma: results in 'invalid cross-device link' when reflinking; mv will fallback to a normal (inefficient) copy.

Possible locations:

/var/log/
/var/lib/libvirt/images/
/var/lib/containers/ ##useful for overlayfs driver, not needed for btrfs driver

Implementation:

Anaconda knows how to do this already, just change the kickstart to add additional subvolumes.