USB 3.0 extremely slow
I have a MacBook Pro with USB 3.0. If I plug a Western Digital My Book drive into it, it's crawlingly slow (100kbps). If I plug a USB 2.0 drive into it, it's as fast as the disk. If I plug the USB 3.0 drive into my older Mac Mini (USB 2.0) it's also as fast as the drive. Why is USB 3.0 so much slower than 2.0?
MacBook Pro with Retina display, OS X Mavericks (10.9)