Copying Files over internal network; USB vs Thunderbolt Ethernet Adapter Speed Issues

Discussion in 'Mac OS X Server, Xserve, and Networking' started by shoebobs, Jan 10, 2015.

  1. shoebobs macrumors regular

    Jul 5, 2008
    I just setup a Mac Mini Server for file sharing/other services. I have noticed an issue I am hoping someone can help explain.

    Setup Details
    • Mac Mini Connected to Ethernet
    • Macbook Air Connected to Ethernet via USB to Ethernet Adapter
    • Apple Airport Extreme with Cisco Gigabit Switch for Networking
    • House wired with Cat6

    When I have the above setup, copying files over the network is extremely slow...looks to be about 5 MB/S. I understand the USB to Ethernet Adapter is only 10/100, but I would expect much higher than 5 MB/s.

    When I switch to the Thunderbolt to Ethernet adapter on my Macbook Air, it is much faster. I don't have exact numbers, but it looked closer to 100 MB/s, which is acceptable for what I need.

    1. Can anybody explain if the speeds with the USB adapter make sense and if this is normal/expected behavior?
    2. If not expected,
    - Is there any setting I need to change on my Mac/Airport/Switch?​
    - Can anybody with a similar setup (two Macs connected via Ethernet over a network) compare performance of the USB vs Thunderbolt adapter? I am wondering if the USB adapter I have is defective.​

    I am really hoping I can find a way to use the USB adapter. I don't like using the Thunderbolt adapter because then I cannot hookup an external monitor to my MBA.

    Any help would be greatly appreciated!
  2. IHelpId10t5 macrumors 6502

    Nov 28, 2014
    At even the theoretical maximum of 100 M(bit)/sec Ethernet of your USB adapter, you could only expect 12.5 M(Byte)/sec transfer. However, due to the overhead of Ethernet and other protocols involved, you can't even expect anything close to that. So, your significant change when using the Gigabit/sec adapter using TB is expected.

    Although I would rarely recommend using WiFi if wired Ethernet is available, if your MBA and wireless router has 802.11n wireless available, you could use that for networking and expect a theoretical 37.5M(Byte)/sec and still have your TB port for the monitor.

    Hopefully, Apple will add at least one more TB port to the next MBA so we don't need to make these tradeoffs.
  3. brentmore macrumors 6502


    Jul 19, 2002
    It comes down to 10/100 vs gigabit and the data rates that you're seeing make sense. There are some USB gigabit adapters on the market, but your theoretical max will be limited by the USB interface. You can also go wireless, as mentioned before.
  4. Altemose macrumors G3


    Mar 26, 2013
    Elkton, Maryland
    If this MacBook Air has USB 3.0, then you could get a third party adapter which is capable of Gigabit speeds over USB.
  5. ShinySteelRobot, Jan 13, 2015
    Last edited: Jan 13, 2015

    ShinySteelRobot macrumors regular


    Jul 22, 2002
    Upper Left Corner, USA
    For comparison, on my home network I get 900 (average) Mbps with the Thunderbolt-to-Gigabit-Ethernet adapter. That's about 112 MB/s.

    When I use the USB-to-Fast-Ethernet adapter I get about 85 Mbps, about 10 MB/s. So your USB speeds seem a little low.

    All the above is on a network with gigabit switching hubs and all Cat6 cable with no cable run longer than 75 ft. This speed was tested between a new MacBook Pro 13 (USB vs Thunderbolt adapters) and a 2011 Mac Pro (native Gigabit Ethernet adapter).

    BTW, I use Speedy Net to measure the speeds between Macs. It makes it trivially easy to test network speed between two Macs. No affiliation with them other than as a happy customer. Makes it easy to test in both directions, too.

    Good luck, hope that helps.
  6. shoebobs thread starter macrumors regular

    Jul 5, 2008
    Thanks for the info, both of you. I see some of my issue was due to confusing bit vs byte :eek:

    Speedy Net is a cool little tool - I appreciate the info on that. I did some tests and was getting similar speeds to you, just a little under 900Mbps on Thunderbolt and a bit under 85 on Apple's USB 2.0 adapter.

    Thanks you so much for suggesting this! I didn't even think of this as an option, but I just got a USB 3.0 adapter in the mail and speeds look to be roughly on par with the Thunderbolt adapter. Now I can have fast transfer speeds when accessing my mini server and not sacrifice my external display :)

    I was close to going and purchasing a Thunderbolt Display for the hub feature that would allow me to gain Gigabit ethernet speeds with the external display. I really need the external display for productivity for work, so I'm really glad you suggested the USB 3.0 adapter. Buying the Thunderbolt Display would not have been a very smart use of money.
  7. Altemose macrumors G3


    Mar 26, 2013
    Elkton, Maryland
    Would you care to link to the adapter you ordered for future reference?
  8. shoebobs thread starter macrumors regular

    Jul 5, 2008
    Here you go -

    Seems to be working great, but I've been using it for less than a day, so not enough time to really now if there are reliability issues. Good reviews on Amazon though. Just make sure you lookup the instructions for how to install the driver and add the adapter to your network listing - as long as you follow that it should be very simple to setup.
  9. unplugme71 macrumors 68030

    May 20, 2011
    10/100 over USB 2 will probably give you 5 or 6 MB/s. Ethernet has overhead, so does the USB interface, and so does the SMB/AFP protocol.

    Gigabit has a max of 125MB/s but I'm able to get around 115-117MB/s using the TB to Gigabit adapter. I might be able to squeeze a bit more if I tune the adapter and network further, but all that work for 2-3MB/s isn't going to be that noticeable anyway.

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