Raspberry Pi 4 once again, just as it’s predecessors, delivers 1.2A max to all USB connectors.
Meaning, since USB 3.0 needs a max of 900mA and USB 2.0 max. 500mA,at max power you can either use ONE USB 3.0 port or TWO USB 2.0 ports.
fonte: https://forum.libreelec.tv/thread/24395-raspberry-pi-4-wd-elements-4tb-external-drive-clicking-from-hdd/?postID=159188#post159188