Transfer speeds with USB 3 vs. TB2

Discussion in 'iMac' started by kat.hayes, May 24, 2017.

  1. kat.hayes macrumors 6502a

    Oct 10, 2011
    Using a 2015 5K iMac:

    1. Is there a way in real time to check the transfer speeds of a Thunderbolt 2 device or a USB 3.1 device when transfer files?

    2. The Apple website indicates that TB2 transfers at 20Gb/s and USB 3.1 transfers at 10Gb/s. Are these realistic speeds when using the proper cables? Should transfer rates always be around these speeds or does it change?

    3. Besides price and the fact that there are more USB 3 devices, are there any reasons to use a USB3 cable vs. a TB2 if given the option?

    Thank you.
  2. keysofanxiety macrumors G3


    Nov 23, 2011
    Depends what you're transferring and where you're transferring it to. If you're copying it to an external HDD then the bottleneck will be limited to the HDD I/O. If you're transferring 100s of little files, it might take longer than one big file.

    Overall the transfer speed cited is the theoretical maximum throughput, so you won't ever hit those speeds with 100% saturation. There are so many elements that could cause speeds to fluctuate; the content, the cable, the drive you're copying from, the drive you're writing to, resource usage on the system, Saturn's alignment with Jupiter, the lot.

    However the speeds should certainly be pretty quick on either USB 3.1 or TB2. It's unlikely you'll find yourself twiddling your thumbs waiting for stuff to copy, put it that way.

    TL;DR: don't worry and use whichever interface suits you best.
  3. cynics macrumors G4

    Jan 8, 2012
    1. If its a mounted storage device you can probably just target the drive with a program like Blackmagic to get a general idea of transfer rates.

    2. No, not even close. There are too many variables. The type of storage media used, that storage medias speed, inherent overhead, the actual data being transferred in relation to the storage media used, the enclosure being used, etc etc.

    3. Besides price and product availability? Not at all, those are the main things that deter people from Thunderbolt solutions.

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