How to limit disk usage

this might be crazy, but I am trasfering lots of large files and I would like to only use about half my systems ability. for example if it is 150 I would like to limit the transfer speed to 75.

the disks are being used by other programs and those activities are more important than a file transfer in the background.

There no way to limit copy speed, except when FTP is involved.

At least not built-in. I’m not sure but there might be 3rd party tools that let you set a process to a lower file I/O priority so that disk requests from other processes get more attention.