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User profile for user: null null416
null null416 Author
User level: Level 2
229 points

macbook air 2018 external drive usb 3.0 - slower ?

Hello there, attached a Western Digital Usb 3.0 drive from a previous MacBook Pro to the new MacBook Air 2018 (for Time Machine Backup and Restore and migration ), its a fairly new drive, roughly 2 years old and USB 3.0 has Been blazingly fast previously, however now on the 2018 MacBook Air its much slower doing "preparing backups" and time machine backups, anyone know whats changed with the Air and External 3.0 Usb drives? Same drive, different MacBooks - much slower results :/


Any tips appreciated


and yes -- same cable

Posted on Jul 31, 2019 1:02 AM

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User profile for user: Tesserax
Tesserax
User level: Level 10
152,302 points

Posted on Jul 31, 2019 10:08 AM

Have you tried running an actual drive throughput speed test ... and not just use Time Machine as your "speed" measurement?


If not, I suggest that you try using either AJA's System Test LIte or Blackmagicdesign's Disk Speed Test to find out the WD drive's throughput performance.


The theoretical top bandwidth for USB 3.0 is 5.0 Gbps (625 MBps). Actual throughput will be lower, especially with HDDs.


FWIW, I have a WD My Book Pro connected directly to 2018 Mac mini using a Thunderbolt 3-to-Thunderbolt 2 adapter. Thunderbolt 2 has a theoretical top bandwidth of 20 Gbps, yet I only get around 350 MBps with this drive. This reduction is due to a number of factors, that include the drive's themselves. The My Book Pro uses HDDs, not SSDs.

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User profile for user: Tesserax
Tesserax
User level: Level 10
152,302 points

Jul 31, 2019 10:08 AM in response to null null416

Have you tried running an actual drive throughput speed test ... and not just use Time Machine as your "speed" measurement?


If not, I suggest that you try using either AJA's System Test LIte or Blackmagicdesign's Disk Speed Test to find out the WD drive's throughput performance.


The theoretical top bandwidth for USB 3.0 is 5.0 Gbps (625 MBps). Actual throughput will be lower, especially with HDDs.


FWIW, I have a WD My Book Pro connected directly to 2018 Mac mini using a Thunderbolt 3-to-Thunderbolt 2 adapter. Thunderbolt 2 has a theoretical top bandwidth of 20 Gbps, yet I only get around 350 MBps with this drive. This reduction is due to a number of factors, that include the drive's themselves. The My Book Pro uses HDDs, not SSDs.

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User profile for user: Tesserax
Tesserax
User level: Level 10
152,302 points

Jul 31, 2019 4:41 PM in response to null null416

Please do post back your results as I'm curious about the results you will get. Do you still have the old MBA that you can run these tests on as well? If so, it would also be interesting to see if the test results match your observations.


The 2018 MacBook Air has two Thunderbolt 3 (USB-C) ports. What type of cable/adapter are you using to connect the external drive? ... and what exact model is your WD drive?

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macbook air 2018 external drive usb 3.0 - slower ?

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