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Slow USB 3.0 speeds from SATA 3 HDD

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?
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  1. Best answer
    Are you using a USB 3.0 port? Your speeds are about right for a USB device at USB 2.0 speeds. Not only that, the hard drive doesn't run at SATA 3 speeds, even though it says it does. It just can't transfer enough to fully use the speed offered by SATA 3.

    Casey
  2. Yep, I double checked, it's in the right port. I know I won't get the 600MB/s, but I've read over and over of people getting at least 60MB/s which is about 3x what I'm getting. I just don't know what my bottleneck is. I dunno if it's a bad cable, bad port, or whatever. I'm about to go to work now but when I get home I'll try my other usb 3 ports, and I'll try a usb 2 cable to see if the speed drops any. Thanks, I'll keep it updated.
  3. I switched usb 3.0 ports and got the same results for both, but noticed something else. My external drive is divided into 2 partitions (2tb and 850gb). When copying to the big partition it goes at a steady usb 2 rate, but copying to the smaller one starts off real fast (like 200 mb/s) but quickly drops to about 30 and seems to freeze after a few seconds, but the file being transferred changes real slowly, like it's really transferring just at slower speeds. I even tried the usb 3.0 ports directly into the motherboard in the back. Same result. I also took a usb 2 cable and connected it, same exact speeds. So I dunno if my usb 3 cable is bad, my external drive, or my motherboard.
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