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NMVe SSD Slow Write Speed Mac M1

I'm using an NMVe SSD with a Thunderbolt 3 enclosure and cable for my Mac Mini M1. The read speed is great at approximately 2,500 MB/s but the write speed is less than half of that. Is there a fix for this?


Setup:

  • WD Black SN750 Gen3 PCIe NMVe SSD
  • Fledging Shell Thunder Thunderbolt 3 Enclosure
  • Belkin Thunderbolt 3 5A Cable / Included Thunderbolt 3 Cable
  • Mac Mini M1

Posted on Aug 30, 2021 5:19 PM

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Posted on Sep 8, 2021 6:44 AM

After testing with various Thunderbolt 3 cables, a Fledging Thunder Shell NMVe Thunderbolt 3 enclosure, an Acasis NMVe Thunderbolt 3 enclosure, a Mac Mini M1, and a Macbook Pro 2018 (Intel), I realized it was the WD Black SN 750 2TB that was the bottleneck.


The lower quality TLC flash was not able to write faster than 1,100 MB/s. Read and write speeds also dropped significantly after a short while of transferring large files while observing data transfer rates in Activity Monitor.


I purchased a Samsung 970 Pro 1TB and tried it with both NMVe enclosures. No matter what combination I used of Thunderbolt 3 cables, enclosures, and devices, I was achieving 2,200 MB/s write and 2,600 MB/s read speeds with consistent high data transfer rates in Activity Monitor. The MLC flash is worth the extra price if you need speed, consistency, and longevity in your workflow.


I was considering purchasing a Samsung 980 Pro because it's cheaper. However, it is also a TLC flash NMVe and due to the limitations of USB 4 and Thunderbolt 3, it will not be able to achieve the incredibly high read and write speeds advertised. Therefore, the Samsung 970 Pro is still the best option.


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Sep 8, 2021 6:44 AM in response to Yungyyyy

After testing with various Thunderbolt 3 cables, a Fledging Thunder Shell NMVe Thunderbolt 3 enclosure, an Acasis NMVe Thunderbolt 3 enclosure, a Mac Mini M1, and a Macbook Pro 2018 (Intel), I realized it was the WD Black SN 750 2TB that was the bottleneck.


The lower quality TLC flash was not able to write faster than 1,100 MB/s. Read and write speeds also dropped significantly after a short while of transferring large files while observing data transfer rates in Activity Monitor.


I purchased a Samsung 970 Pro 1TB and tried it with both NMVe enclosures. No matter what combination I used of Thunderbolt 3 cables, enclosures, and devices, I was achieving 2,200 MB/s write and 2,600 MB/s read speeds with consistent high data transfer rates in Activity Monitor. The MLC flash is worth the extra price if you need speed, consistency, and longevity in your workflow.


I was considering purchasing a Samsung 980 Pro because it's cheaper. However, it is also a TLC flash NMVe and due to the limitations of USB 4 and Thunderbolt 3, it will not be able to achieve the incredibly high read and write speeds advertised. Therefore, the Samsung 970 Pro is still the best option.


Aug 31, 2021 1:45 PM in response to Yungyyyy

I have the same problem with my RABRENT Rocket XTRM-Q 2TB!


Write speed at about 1350 to 1450 and read at over 2600 MB/s

That's far less than on any other device I own.


Here some prominent reviews, but sadly all on Windows:


https://www.tweaktown.com/reviews/9527/sabrent-rocket-xtrm-2tb-portable-ssd/index.html

https://lanoc.org/review/storage/8121-sabrent-rocket-xtrm-q-thunderbolt-3-2tb?showall=1

https://www.tomshardware.com/reviews/sabrent-rocket-xtrm-q-portable-ssd-review

https://the-gadgeteer.com/2020/09/03/sabrent-rocket-xtrm-q-usb-3-2-thunderbolt-3-ssd-review/



The M1 have a general problem with external disks, regardless of vendor or protocol used (USB 3.x, USB4 or Thunderbolt).

As seen in https://discussions.apple.com/thread/253087674 Apple dropped support for at least one USB 3.x protocol, which halves the performance of such drives.


I am still somewhat happy with my M1, but I will not buy more of them, hoping for M1X or M2 to get better.


Aug 30, 2021 10:04 PM in response to Yungyyyy

It won’t. Be aware that there’s a bit of a racket with over-spec’ed/over-marketed drives and enclosures not delivering, followed by a predictable blame game targeting Apple. If you’re in a position to return the drive & enclosure for full refund, I would do so. You’re looking for solutions, not blame games, which, sadly, is the current state of the market.

Aug 31, 2021 4:19 AM in response to Yungyyyy

I do not believe it is the WD drive. I have several NVME WD drives (blue and black). Mine are all using Trebleet enclosures. I get 2161/2700 w/r speeds using any number of TB cables. This is through a hub (are somewhat faster connected directly to my Mac). I would guess it is the enclosure. Before I purchased my enclosure I found various reports that indicated different speeds based on design. I get these speeds on both my 2019 Intel iMac and my MacBook Air M1 so you should see similar on your Mac Mini M1.

NMVe SSD Slow Write Speed Mac M1

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