Very slow USB hard drive speeds on new Mac mini

TheGreatDave

macrumors newbie
Original poster
Jun 11, 2013
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I have two USB 3.0 hard drives connected straight into the Mac mini. Blackmagic Disk Speed is giving me 83MB/s read on one drive and 180MB/s on the other. They're both brand new drives, 5Tb Seagate and Toshiba's respectively. Is there any troubleshooting steps I can take to understand why I'm getting such mediocre speeds, especially on the Seagate?
 

HDFan

macrumors 65816
Jun 30, 2007
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I have two USB 3.0 hard drives connected straight into the Mac mini. Blackmagic Disk Speed is giving me 83MB/s read on one drive and 180MB/s on the other.
What speeds were you expecting? 180 MB/s for a single hard disk is excellent. My last USB 3 single disk test on a (slow) Seagate Backup plus disk was 75.6 MB/s write, 82.5 MB/s read. For anything faster you need to go to SSD or RAID.
 
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TheGreatDave

macrumors newbie
Original poster
Jun 11, 2013
17
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What speeds were you expecting? 180 MB/s for a single hard disk is excellent. My last USB 3 single disk test on a (slow) Seagate Backup plus disk was 75.6 MB/s write, 82.5 MB/s read. For anything faster you need to go to SSD or RAID.
It's the discrepancy that's confusing me. The Seagate is brand new out the box, doesn't need a power source yet it's getting less than half the speed of another drive. I can't think of a logical reason for it so I'm wondering if there's any sort of troubleshooting that could explain it.
 

tubedogg

macrumors regular
Dec 18, 2003
190
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Minnesota
The Seagate is brand new out the box, doesn't need a power source ...
The fact that it doesn't need a power source would indicate to me it's a lower-performance drive. Just saying Seagate and Toshiba doesn't say anything about what kind of drives they are. A 10K RPM performance hard drive is going to have much better performance than a 5400 RPM laptop-class drive.
 

Cheapassmac

macrumors regular
Nov 5, 2018
210
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It's the discrepancy that's confusing me. The Seagate is brand new out the box, doesn't need a power source yet it's getting less than half the speed of another drive. I can't think of a logical reason for it so I'm wondering if there's any sort of troubleshooting that could explain it.
This doesn't apply to SSDs, but bus powered hard drives are generally slower than powered. Does the bus powered one have the option to connect an optional AC adaptor or a 2nd USB? You might get better performance if that was the case.
 

chabig

macrumors 603
Sep 6, 2002
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Since the Toshiba/Seagate ratio is almost 2:1, it sounds like the Toshiba might be 10Gbps USB while the Seagate is 5Gbps. You would need to check the drive specs to find out for sure.
 

Cheapassmac

macrumors regular
Nov 5, 2018
210
134
Since the Toshiba/Seagate ratio is almost 2:1, it sounds like the Toshiba might be 10Gbps USB while the Seagate is 5Gbps. You would need to check the drive specs to find out for sure.
Nice thought, but even 5Gbps is 625 megabytes per second. Physical power of the bus might be more of a factor.
 

ktcifone

macrumors member
Oct 30, 2009
48
27
done some speed tests.
1- 4 8TB 5400rpm drives raid5 tb2 array own USBc port with adapter - 470mb/sec
internal ssd 1.9GB sec.
random SATA drive on usb3 95MB/sec (thunderbolt2 dock with 10ft cable)
waiting for the usbc 3.0 hub to get better comparisons.

since there appears to be 2 controllers split the high demand connections
ports 0-2 - high demand
ports 1-3 - low demand

should get good results.
 
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