Thank you Dominic for your quick response. But I had already reviewed this page and it does not solve my problem. The ABOUT THIS MAC info says the drives are connecting at a maximum potential of 5Gbit/s and they do reside on the USB 3.0 interface (as compared to my HP Speakers or mouse which connect at USB 2.0 speeds).
I am having the exact same issue on my 2013 MBPr.
I have two Seagate GoFlex USB 3.0s, one plugged into the regular 3.0 port (450MB/s) on the left and the other plugged into the high-speed (5GB/s) 3.0 port on the right. When doing a simple copy/paste from the one drive to the other, I observe the following speeds:
Peak Read (USB 3.0): 36.2Mb/s (288Mbit/s)
Peak Write (USB-HS 3.0): 48.7Mb/s (384Mbit/s)
This is far below the 620MB/s for 3.0 and is more around the 35MB/s USB 2.0 standard.
So, I'm likely to agree with the original compaintant that the 3.0 standards aren't being employed by the MacOSX USB drivers and I'd hope to see a fix soon for these issues lest people start moving off of the Mac platforms to other vendors who adhere to industry guidelines.
I have the same issue on my company's MacBook Pro 9.1 (mid 2012).
USB 3 is extremely slow.
I usually connect SSD via USB-to-SATA adapter. I also have SSD inside the macbook.
If I perform plain old dd-copy (dd if=/dev/diskX of=disk_image.raw) I get ~23 MB/s transfer speed. I've tried several USB3 drives and it gave me the same terribly slow speed.
Dear Apple, please make an effort to solve this problem.
What happens if you eject the drive in OSX pull the USB 3.0 cable out then replug in?
For me when booting up it registers my USB 3.0 HDD at USB 2.0 speeds but if I eject then replug back in the speeds will go up to USB 3.0.
I checked System Information and in the USB panel it would say my HDD is registered to the High-Speed bus but if I unplug then re-insert it becomes Super-Speed bus. Its an annoying bug that Apple never seem to acknowledge and probably has something to do with the OS starting up and USB 3.0 connections.