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User profile for user: pb20
pb20 Author
User level: Level 1
12 points

Slow Transfer Speed Between Samsung T7 External SSD & Mac Pro 2013

I bought a Samsung T7 external ssd for data backups for my Mac Pro 2013. The external drive is a 3.2 v2 usb c drive, and I have it connected to a usb 3.0 port on the back of my Mac Pro. Apparently the max bandwidth speed of a usb 3.0 port is around 600 - 625 MB/s, however using Blackmagic disc speed test I seem to only be getting around 355 MB/s read and write. I'm just trying to figure out why this is. The Samsung SSD is capable of around 1000 MB/s transfer speeds so I know its not the limitations of the SSD holding it back. I know I won't be getting that stated figure because of the limited speed of the 3.0 port on the Mac Pro but I thought I would be at least getting close to its max speed of around 600 MB/s. Any insight would be very grateful.

Mac Pro, macOS 10.15

Posted on Jan 11, 2021 5:47 AM

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
133,333 points

Posted on Jan 12, 2021 6:53 AM

Are you using a USB-3 rated cable? These would tend to have a blue plastic insert, indicating the presence of the additional conductors REQUIRED for USB-3 speeds.


Have you tried a different USB-3 cable? the ones shipped in the box are often "lowest bidder" cables.






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User profile for user: pb20
pb20 Author
User level: Level 1
12 points

Jan 12, 2021 4:54 AM in response to Grant Bennet-Alder

Hi, Thanks for the message. I had a look and the drive is on the same bus as my wired apple mouse, however when I unplug all other devices from the usb ports the data speed is still slow. I read somewhere that if the first thing you plug into the usb ports is a usb 2.0 device, all other devices plugged in after that will be at 2.0 speeds. Don't know if this is true or not but I unplugged everything anyway, rebooted the computer and plugged the external ssd drive in first. This also didn't change the speed at all.


I did notice however in the 'System Information' that my Samsung T7 ssd is using quite a lot of power from that bus. It says current required (mA) 896 and current available from that port is 900 mA. So it's nearly maxing out the power supplied to it. Do you think this power usage may be interfering with the speed of the ssd and slowing it down? Maybe the drive being bus powered may be bottlenecking the transfer speed.


The only other thing I've noticed in the System Information that is using quite a bit of power is the 'Keyboard Hub' which requires 300 mA and it's 'speed' is up to 480Mb/s. The keyboard itself isn't, but the Keyboard hub is. I've inserted a picture below of what my System Information page looks like. My Audient audio interface is connected to one of the ports but even when it isn't connected it doesn't change the speed at all.


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Slow Transfer Speed Between Samsung T7 External SSD & Mac Pro 2013

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