Re: Large files for relations

On Wed, May 3, 2023 at 5:21 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> rsync --link-dest

I wonder if rsync will grow a mode that can use copy_file_range() to
share blocks with a reference file (= previous backup). Something
like --copy-range-dest. That'd work for large-file relations
(assuming a file system that has block sharing, like XFS and ZFS).
You wouldn't get the "mtime is enough, I don't even need to read the
bytes" optimisation, which I assume makes all database hackers feel a
bit queasy anyway, but you'd get the space savings via the usual
rolling checksum or a cheaper version that only looks for strong
checksum matches at the same offset, or whatever other tricks rsync
might have up its sleeve.