I'm aware of the comments saying rsync or rclone, and I absolutely also use those, but for initial migrations I often find myself simply using tar instead.

Something like :

    (cd /src/dir && tar cf -) | ssh user@host "(cd /dst/dir && tar xvf -)" 

It won't saturate 4 multichannel links, you'll most likely need rclone or rsync for that (or robocopy it appears), but it's much faster than rsync on initial copies.

Then for good measure, once the tar copy finishes, I run a single rsync verification between the two targets.

That being said, my latest storage migration was performed using either ChronoSync or Carbon Copy Cloner from my Mac mini server. They won't do anything rsync cannot already do, except present data and copy history in a graphical environment.