Why slow transfer rate?

I just purchased the Plugable 7 port USB 3 hub and am in the process copying 546 gb of data from a 3 TB USB 3 Seagate external drive which is plugged directly into my ASUS CM6850 PC - 3.7 Ghz - Win 7 USB3 port, to a 2 TB USB 3 Seagate external drive plugged into the Plugable 7 port hub, which is plugged into the 2nd USB 3 port in the back of the pc.

My transfer rate is running from 16-40 mb/s.

The transfer rate seems to be very slow as compared to what I expected.

Does anyone have any suggestions to improve performance, or was I just execting too much in the first place?

Hi Loren,

Thanks for posting your question here. I’ll be happy to help. Isolating problems with transfer times can be a bit tricky, especially when there many variables involved. For a large transfer there’s the time for the data to be read, combined with the other disk usage of the computer that plays a major role.

If you want to get some raw numbers on each component of your setup to compare and possibly find the one that’s introducing a lag first get a disk benchmark program like ATTO.


Then run a test on the disk connected to a USB 2.0 port, a USB 3.0 port, and a USB 3.0 port with USB 3.0 hub.

To get a good perspective of the USB disk you are writting, compare similar data points from another USB disk.

If you see a big drop in transfer speed at any stage, you’ll have a place to start troubleshooting. My suspicion is however, if you were to connect a USB 2.0 drive to the same setup, or use a USB 2.0 cable somewhere in the chain you would see anywhere from 5-20 Mb/s so it may be more of an overhead issue and your USB 3.0 setup is going much faster but still not approaching it’s maximum.

I hope this helps.

Thank you. I’ll do exactly that.

It’s important for me to learn where the bottleneck is because the amount of data is so large it was taking 12+ hrs to backup everything via USB2. As a result, my backups were getting more and more infrequent.

I need the best USB 3 can give me if I’m going to do the backups as often as I really should.

I’ll get back to you if I have more questions.

Thanks again,


Hi Loren,

We’ve seen quite a bit of variability between drives as well and have had great results with some Hitachi 4TB drives.

Let me know your results and we’ll do what we can to help.


  1. Of course you are correct. Regardless of what I expected, it is still faster than USB 2.

  2. I haven’t finished the benchmark tests yet but it does look like the 2 TB drive is much slower than the 3 TB. Just plugged directly into the pc, the 3 TB runs about 140mps and the 2 TB drive max’s out at 100mps.

Since I have 2 USB 3 ports on the pc, I have to ask— if I’m going to copy hundreds of GB from one external drive to another, wouldn’t the fastest of all options be to have both external drives plugged directly into the pc ports? In other words, does the 7 port hub have any overhead that would make it slower than directly into the pc?

Hi Loren,

Thanks for taking those steps I’m glad that the numbers are reasonable. The hub shouldn’t introduce much overhead, most likely the drive speed and other activity on the computer will have a larger effect.

You may see a difference in performance if the 2 USB 3.0 ports are actually different host controllers inside the machine, then they would have two separate links to the PCI bus instead of sharing one which could make large transfers faster. It’s most likely they are on one controller though. You can tell by looking for one or two USB 3.0 host controllers.

Let me know if there’s anything else I can help with.


Thanks again for the quick and informative reply.

There are two major reasons why your USB transfer speed can be too slow.

  1. Your device is connected in USB 2.0 mode. It happens quite often with USB 3.0 devices. To check it, download PC-Wizard (http://www.cpuid.com/softwares/pc-wiz…). Start application and select “IO Ports”. Find your device in lower pane and check “USB Version:” line. If it is 2.0, this is the problem.

  2. You transfer small files. Because of high latency, this is inherent flaw of USB buses. For example, if I transfer 4 kBytes files to/from my USB3 Seagate GoFlex 2 TB drive, speed is 23 MBytes/Second. If I transfer 100 MBytes files, speed increases to 110 MBytes/Second.

Oleg, probably because this ASUS CM6850 has 2 USB 3 ports in the back,
2 USB 2 ports also in the back, 4 USB 2 ports in the front, and a built-in card reader I was getting confused reading PC-Wizard. So in order to be safe, I shut down the PC, then unplugged my Seagate GoFlex 3 Tb drive from it’s normal home in the USB 3 port at the back of the PC, and plugged it into your 7 port hub. When I rebooted, the hub light turned blue over the port it was plugged into, but my PC did not see the drive. Windows explorer did not show it. (Win 7)

I then shut down again and plugged the external drive back into the USB 3 port in the back of the pc, rebooted, and the drive showed up again.

I have to admit, I had this problem with a 4 port USB 3 hub I purchased from a different company and returned the hub because I thought it was defective. Now I’m begining to see that there is something else going on that I don’t understand.

"Find your device in lower pane and check “USB Version:” line.
If it is 2.0, this is the problem. "

If I do find that to be the problem, how do I correct it?

Hi Loren,

I’ll be happy to continue to work with you on getting your hub working. To avoid any confusion, please contact us at support@plugable.com with your Amazon Order Id, a link to this thread and a description of the current symptoms you having and we’ll be happy to help.


Plugable Technologies