I'm copying a bunch of files from an internal HDD to an external one with USB 3 but am only getting around a steady 22.5 MB/s. The internal hdd is a Seagate Barracuda (ST2000DM001) 7200 RPM SATA 3 drive. The external is a Hitachi Desk Touro Pro (HTOLDNB30001BBB) 7200 RPM USB 3.0 drive. So what gives?