File Transfers Over Thunderbolt Start Fast Then Slow Down

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File Transfers Over Thunderbolt Start Fast Then Slow Down

Just like the title says. I'm trying to transfer 1.5 TB of data from one external drive to another. It usually starts off at 1600MB/s for the first 5 to 10 minutes, then slows down to a crawl anywhere from 8MB/s to 75MB/s.

I've tried the folllowing:

Restarting computer cold and hard boots.
Connecting nothing else to the Thunderbolt other than drives
Using different TB3/TB4 enclosures,
Using different TB4 cables
Using a TB4 hub
Connecting each ext enclosure direct to the Mac Mini M1 (late 2020)
Using Finder to commence transfer
Using Terminal to commence transfer
Upgrading from Monterey to Sonoma

Overheating is not an issue either as I've implemented both active and passive cooling methods with no improvement in performance.

Current NVME drives used:

Seagate Firecuda 510 2TB
Corsair MP600 Core XT 4TB

Speeds:

To conclude, the transfer speeds on this M1 Mac Mini have be inconsistent since day one and is absolutely aggravating considering the amount of time and money I've put into methodically testing and troubleshooting.

Mac mini

Posted on Oct 14, 2023 6:38 AM

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Answer 1

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shakefists Author

Level 1

10 points

Oct 14, 2023 4:30 PM in response to tbirdvet

Hi,

After running a few trials today with the transfer, I've found that the slowdown consistently happens when the transfer completes 960 MB. It hits that and it slows down. If it were a heat issue, there would be a variance.

After testing a couple of more nvme drives, I've found great results with no slowdown when going from Crucial to Seagate and from Seagate to Corsair. But Crucial to Corsair was exhibiting severe performance issues. The Seagate to Corsair would vary between 1900 and 2500. I'm happier with that. Nothing special with thermal other than a surface mounted heatsink on the aluminum enclosure to increase surface area.

With all that said... Since the beginning the Seagate Firecuda 510 2TB has almost always been a great performer.

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Answer 2

BDAqua

Level 10

250,259 points

Oct 14, 2023 7:05 AM in response to shakefists

To get a beter pictue... We need to see what all is running, a report from this will not display any personal info...

Using EtreCheck - Apple Community

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Thanks for Old Toad’s etrecheck instructions…

Slow iMac 2017 - Apple Community

Use the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck. In a Reply before you click post, look for this to add longer texts...

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Answer 3

tbirdvet

Level 6

17,307 points

Oct 15, 2023 5:00 AM in response to shakefists

I have found testing several NVME drives that not all perform the same with a Mac. Samsung 960 MVME runs much slower than my WD NVME. This has been confirmed by many users so yes certain drives/combination of drives is critical for transfer speeds.

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Answer 4

shakefists Author

Level 1

10 points

Oct 14, 2023 8:59 AM in response to den.thed

Hi Den.Thed,

Thank for your response. Both drives are formatted using APFS. I'm not trying to copy the entire drive, per se, rather just a folder off the drive.

I recently opened up a case with apple, and we spent some time on the phone with an escalation to a higher tier of support, however he didn't have much to offer after monitoring transfers in both Safe mode and in a new user profile. He did confirm the anomaly.

Oddly enough, in the new user profile this weird thing happens...

Start the transfer, top speeds ensue, then after a couple of minute it slows down to a crawl every 25 seconds for 5 seconds, then bumps back up to top speeds. So 25 seconds fast, 5 seconds slow, 25 seconds fast, 5 slow. Eventually it slows permanently.

It was my understanding the the Mac Mini M1 is running 2 TB busses, not 1 as you see below and verify with several Mac Mini m1 reviews. With that said, there shouldn't be any "saturation". The transfer runs at 1400MB/s for the first 900GB or so... then slows to 50 MB/s.

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Answer 5

den.thed

Level 10

92,560 points

Oct 14, 2023 9:14 AM in response to shakefists

shakefists wrote:

Hi Den.Thed,

Thank for your response. Both drives are formatted using APFS. I'm not trying to copy the entire drive, per se, rather just a folder off the drive.

Just checking, thanks.

I recently opened up a case with apple, and we spent some time on the phone with an escalation to a higher tier of support, however he didn't have much to offer after monitoring transfers in both Safe mode and in a new user profile. He did confirm the anomaly.

Oddly enough, in the new user profile this weird thing happens...

Start the transfer, top speeds ensue, then after a couple of minute it slows down to a crawl every 25 seconds for 5 seconds, then bumps back up to top speeds. So 25 seconds fast, 5 seconds slow, 25 seconds fast, 5 slow. Eventually it slows permanently.

All I can add, is that I've seen the same (run fast, rest, run fast) speed variations while doing large copy jobs for years.

It was my understanding the the Mac Mini M1 is running 2 TB busses, not 1 as you see below and verify with several Mac Mini m1 reviews. With that said, there shouldn't be any "saturation". The transfer runs at 1400MB/s for the first 900GB or so... then slows to 50 MB/s.

Sorry, my bad on the Bus configuration.

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Answer 6

shakefists Author

Level 1

10 points

Oct 14, 2023 9:21 AM in response to den.thed

Whats odd is it's fast for the first 900GC then it crawls permanently after the first 900GB or so. What's even more interesting is the 25/5 thing on the new user account. I wonder why that interval and what's causing it. Thanks again for the insight.

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Answer 7

shakefists Author

Level 1

10 points

Oct 14, 2023 9:17 AM in response to BDAqua

Attached is the report requested. Let me know if I missed anything. Thanks for the assistance.

EtreCheck Report

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Answer 8

tbirdvet

Level 6

17,307 points

Oct 14, 2023 4:18 PM in response to shakefists

As you know NVME drives can get very hot. Even though you have tested cooling methods they may not always work well enough to prevent the transfer speed to slow to protect the drive.

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Answer 9

den.thed

Level 10

92,560 points

Oct 14, 2023 8:46 AM in response to shakefists

How are the SSDs formatted and what type of data are you copying.

Instead of using Finder, maybe try using CarbonCopyCloner or SuperDuper.

https://bombich.com/ or https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html

Also keep in mind that the two TB Port M1 Mac mini only has one TB bus, which could easily become saturated and slow down. If that is the case, then another solution might be to connect one SSD to a TB port, one SSD to a USB-3 port and live with +or- 500MB/s.

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File Transfers Over Thunderbolt Start Fast Then Slow Down

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