Painfully slow data transfer to USB 3 devices on 2012 MacBook Air

Discussion in 'MacBook Air' started by Narial Taster, Aug 17, 2012.

  1. Narial Taster macrumors member

    May 17, 2011
    I have a new 13" MacBook Air and found the data transfer speeds to external USB 3 devices to be underwhelming. I ran Blackmagic Disk Speed Test and the results speak for themselves. My 16GB USB 3 flash drive managed a paltry 16 MB/s write speed and a 66 MB/s read speed (Thumbnail attached.) A USB 3 1 TB WD Elements fared slightly better with both read and write speeds averaging at around 65 MB/s.

    Could there be a hardware/ software problem with my computer or one of the drives? FYI, my internal drive has 400 MB/s read and 450 MB/s write speeds. Is this normal? And if not then can you guys think of a fix?

    Attached Files:

  2. kierennyc macrumors regular

    Dec 3, 2008
    The bottle neck could be the actual devices you're transferring to.

    Remember even though the external hard drive is USB 3, it can still only write or read as fast as the spinning platter allows. The same applies to memory sticks - they have their limits too.

    The only way I believe to experience USB 3 at its best is to use SSD drives in a USB enclosure. But of course that isnt cheap or even necessary in most instances.
  3. gnasher729 macrumors P6


    Nov 25, 2005
  4. filmbuff macrumors 6502a


    Jan 5, 2011
    I had a problem a transferring data when I first started using my Mac where speeds would start out fast (50-100 MBps) then grind to a halt and only transfer at 5-10MBps. The problem turned out to be something wrong with the permissions on drives partitioned by Windows (I had been using them on my Windows PC before). Erasing the drives and reformatting them in Disk Utility completely solved the problem.

    I have a 500GB Momentus XT in a Rocketfish enclosure that gets ~90MBps and a Toshiba 1TB portable drive that gets 110MBps! USB 3 is fast when it's working.
  5. Narial Taster thread starter macrumors member

    May 17, 2011
    Thank you all for your replies. I reformatted my flash drive as Mac OS Extended (Journaled) but the write/read speeds remain unchanged (16/65 MB/s). I was wondering if any of you have any experience with a USB 3 flash drive on the June 2012 Macs. If so then it would be great to compare the results.
  6. carlos00 macrumors newbie

    Jul 17, 2012
    The problem is with the flash drive as max write speed are usually much lower than read or regular external HD's.
    The Flash drive you have probably has an max write speed of 16MB/s - have you checked this against the specs of the flash drive?
  7. Narial Taster thread starter macrumors member

    May 17, 2011
    You are right carlos00, the speeds that I am getting are in line with the specs of the flash drive. I was expecting a huge speed boost with USB 3. Thanks for clearing it up. However, I am curious as to why flash drives are slower than regular external hard drives. Shouldn't they be faster as they don't have moving parts?
  8. DrivinWest macrumors regular

    Jun 17, 2007
    Republic of Texas
    I'm in the same boat with a brand new MacBook Air running Mountain Lion.


    This is frustrating to say the least.
  9. SpoekGTi macrumors regular

    Jul 2, 2012
    The Netherlands
    This is not uncommon, cause your iPhoto library which tells you is 91 GB is in fact just a build up from all your photo's......which in your case would around the 26K photos consist which your drive (USB, TB, LAN or even fiber optic) cannot copy faster because it's just too many smaller files.

    If you copy a real 91GB file you should be able to get higher throughputs
  10. KPOM macrumors G5

    Oct 23, 2010
    Flash drives often use cheaper NAND to keep the price down. With some searching, you can find better drives with higher write speeds. Some of the better ones here have write speeds around 70MB/s, which is roughly on par with a platter hard drive.

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