> Tools like ddrescue have the option to first read a disk's filesystem metadata to build a map; and then use that map to only bother to read used sectors, skipping the unused ones.
I don't know how many versions of "ddrescue" there might be, but GNU ddrescue doesn't know anything about filesystems.
The "map" file is just a list of device LBAs (extents) and recovery status.
I've seen a tool for NFTS that can pre-populate a GNU ddrescue map file with unused extents to avoid ddrescue reads of unused areas, but you have to find this tool and manage it yourself.
I don't know how many versions of "ddrescue" there might be, but GNU ddrescue doesn't know anything about filesystems.
The "map" file is just a list of device LBAs (extents) and recovery status.
I've seen a tool for NFTS that can pre-populate a GNU ddrescue map file with unused extents to avoid ddrescue reads of unused areas, but you have to find this tool and manage it yourself.