12" MacBook, transferring files between two 2.5" external hard drives possible?

Discussion in 'MacBook' started by M-1, Nov 11, 2018.

  1. M-1, Nov 11, 2018
    Last edited: Nov 11, 2018

    M-1 macrumors newbie

    Mar 5, 2010
    Can someone answer if this actually reliably works? I don't know if it's the usb-c hub that I have that doesn't allow it but when I try to plug in two 2.5" external hard drives into the hub that's plugged into 1 usb-c port on a MacBook Pro, it is capable of reading both drives but the moment I try to transfer files from one hard drive to another, 1 of them fails and ejects due what I believe is a lack of power. Knowing this, I simply plug in the hard drives into individual ports but this of course is not possible on the MacBook with only 1 usb-c port. It seems like a huge oversight if the MacBook is not capable of powering two 2.5" drives off of one usb-c port. Then again, maybe it can and it's just the hub that I am using. (Satechi TYPE-C MULTI-PORT ADAPTER 4K WITH ETHERNET V2)

    Has anyone been able to successfully transfer a large amount of files between 2 bus powered hard drives using a usb-c hub plugged into 1 usb-c port of the 12" MacBook? If so, which hub are you using?
  2. chabig macrumors 603

    Sep 6, 2002
    It might not work off the MacBook's battery, and I wouldn't necessarily expect the computer's battery to power two external hard drives. Confirm that you connected the hub to power? And if the answer is no, plug you MacBook power adapter into the hub and try again.
  3. M-1, Nov 11, 2018
    Last edited: Nov 11, 2018

    M-1 thread starter macrumors newbie

    Mar 5, 2010
    It shouldn't be about the MacBook's battery but the USB-C ports current output and the power draw of an external hard drive. A MacBook Pro with 4 usb-c ports is capable of powering 4 individual external SSD's or 2.5" hard drives just fine while running on its battery. It has nothing to do with the MacBook's battery but the usb-c port power output.

    From my understanding USB 2.0 provides a max current of 500 ma, USB 3.1 provides 900 mA and USB-C provides 3000 mA / 3.0 A.

    Typically a 2.5" external USB 3.1 hard drive shouldn't draw more than 900 mA. That's a total of 1800 mA for 2 drives. So a USB-C port should be capable of powering two external bus powered hard drives just fine?

    The hub is a bus powered hub as these hard drives do not require an extra power supply like 3.5" hard drives do. I was of the belief that the hub should be able to draw enough power from the USB-C port. I'll have to check again if using usb-c pass through charging on the hub makes a difference but I don't believe it did or will.
  4. chabig macrumors 603

    Sep 6, 2002
    I thought you were talking about a MacBook with a single USB-C port.

    Anyway, I agree with you that a single USB-C port should probably provide enough power. But if it doesn't, pass-through charging should solve the problem. I'm curious to know if it works. There is no reason the computer should not be able to copy files between two attached drives.
  5. M-1 thread starter macrumors newbie

    Mar 5, 2010
    I am asking about the MacBook. Was just saying as an example in comparing with the MacBook Pro.

    I don't have a 12" MacBook yet but did some more testing now using the hub with 1 usb-c port on a MacBook Pro. One usb-c port on either Mac should be the same in terms of USB 3.1 functionality.

    I was able to attach two external 2.5" hard drives just fine, files were readable on both. I transferred some files between the drives and all looked fine. I tried it twice, once with pass through charging and once without and the macbook pro just running off its own battery.

    I then decided to insert an SD card into the hub in addition to the two ehdd's while running off battery. They were all simultaneously transferring files between each other and kept up. Then suddenly after a few minutes one of the hard drives made a chirping sound as if power wasn't enough and all the transfers paused. Strangely enough the drive was still mounted on the desktop this time. I however promptly cancelled the transfers in case of any read/write damage.

    I will have to do a bit of trial and error to figure out what's going on, whether it's the usb-c port itself, the hub, a faulty usb 3.1 cable or one of the drives. I however tested with some different hard drives and cables, same story. It seems a bit random. When it happens it happens a few minutes in while transferring files.

    Does anyone know for certain if one USB-C port should technically be able to provide enough power to two or even three external bus powered drives? From what I understand, it should. Just curious about other MacBook owners experiences with this. Thanks for any feedback.
  6. EugW macrumors 603


    Jun 18, 2017
    This is my hub:

    Anble USB Type C to HDMI 4K,... https://www.amazon.ca/dp/B071CM5CTG?ref=yo_pop_ma_swf

    Bus power? I don’t even bother trying transferring between two drives. Too risky.

    Test: Single 135 MB file. Power passthrough with my Samsung T5 SSD and my Toshiba HD connected through the Anble hub with USB 3.

    From the MacBook to either of these drives was instantaneous.

    From the Toshiba HD to the Samsung T5 was also instantaneous.

    From the Samsung T5 to the Toshiba HD took just about forever however. After several minutes it still was not complete. So I stopped the transfer and just the process of stopping took a couple of minutes too. WTF.

    Conclusion: Hit and miss transferring from one external drive to another through one port even on external power.

    It seems the safest way to do this would be to transfer to the MacBook first and then retransfer to the 2nd drive. Luckily the above two drive scenario is not something I normally need to deal with. Still, Apple needs to release a MacBook with two independent USB-C (and Thunderbolt) ports.

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5 November 11, 2018