One of the YouTube comments pointed out the issue is most likely the lack of support for SMB Direct (RDMA) in macOS. Would be nice to repeat the test on a Windows/Linux laptop.
It’s crazy that the Ethernet chips consume more power (presumably - because of the heat) than the processor in the computer. How is driving 25Gb/s such a hot task compared to driving multiple 40Gb/s Thunderbolt ports?
Somewhat off-topic: has anyone implemented USB C based networking?
So for instance you have two or more machines that have USB 4 ports at 20 to 80 Gbps and you plug in the appropriate USB C cables to connect them.
What do you need to make the connections appear as a (point to point) part of a regular TCP/IP network? Seems much cheaper than Ethernet if you already have the ports.
ProRes is a compressed and encoded format. In order to become ProRes, it needs to be uncompressed and decoded at some point. uncompressed and unencoded is easier to work with on the rendering side, but much heavier on the data side. Ask your AI about the DPX file format.
Dang, here I was feeling slick with 10Gb between my MBP and Mac mini and NAS. That’s the thing, it could always be bigger / faster / more. It’s enough for my workflow, but it’s fun to see people push further.
As mentioned in the blog post's footnote, the bottleneck may just be on the NAS side:
> this real-world speed limitation could also be related to my use of my lower-power Arm NAS (running on Ampere Altra, with 32 fairly-slow CPU cores). I was testing writing to an array of fast enterprise NVMe SSDs, so they shouldn't be the bottleneck here.
He was only getting 1 Gigabyte of throughput out of the built in 10 Gigabit Ethernet connection and moving to the 25 Gigabit connection only made a marginal impact on throughput, after all.
I'm using the sonnet at work. Work paid for it. Yes it's more expensive. I have gotten over 25 gbps bidirectional, but not by much. Maybe 27. A big downside is that it only supports 15W upstream power which I didn't think to check, so since that laptop only has 2 usb-c ports for power input, it's a bit limiting.
The upside, though, was that I plugged it in, got my throughput, and never had to worry ever again. Remember that engineering time is mucho $$. So troubleshooting overheating, divising a solution, manufacturing it, etc, that all eats into the savings.
The $400 dock would be cool though. It seems smaller than the sonnet and fixes my charging problem. Weirdly I didn't think I'd care about not including transceivers but they did actually come in handy, so that is a downside. Might try to get one of these if I need another one in the future.
Asking out of curiosity because I always wanted but never needed such speeds, could you elaborate on what you do and how does this speed help you? And I presume there’s a reason you’re not able to connect directly to the drives etc. with thunderbolt.
> I can edit 4K video straight off my NAS over the network,
Nothing against Jeff Geerling and I love his YouTube channel and I'm glad he's one of us HNer but this crop of circular "I make YouTube vids about big tx speeds and big NAS because I make vids hence I need big tx speeds and big NAS so I can speak about big tx speeds and big NAS because I make YouTube vids about big tx speeds and big NAS" videos is a bit tiring IMO.
I'm not into cryptocurrencies but, I don't know, host a full Ethereum node, host a Plex/Jellyfin server serving thousands of movies, host LLMs, etc.
I mean: talk about something else than editing vids because you make vids about vids.
For us <25Gbps plebes out there: For god's sake do not buy a USB-C RealTek RTL8156-equipped multi-gig ethernet dongle to use with your Mac. I went through 3, and they're all trash:
Plugable 2.5G USB-C to ethernet adapter (bought November 2025), SABRENT USB C to 2.5Gbps ethernet adapter (bought October 2024), UGREEN USB C 2.5G ethernet adapter (also October 2024). In my experience they immediately fall on their face in a speedtest and drop to a couple hundred Mbps, experience packet loss, etc. This is testing across a few modern Apple Silicon Macs.
I now have a WavLink WL-NWU341G 5Gbps dongle with the RTL-8157 that seems to work well, but I've only run a couple of tests-- I am away from my home setup and don't have wired ethernet run to all the rooms where I'm living.
If you do some Googling, there's some good information out there about it, but when I bought the bad ones, I couldn't find any information corroborating my experience.
For my Macs, the IOCrest USB4 adapters with the AQC113 chipset have been rock-solid and can saturate my 10Gbe network. They do run hot but no stability issues. That's what I use and recommend.
The newer RTL8159 based dongles are smaller, cheaper, cooler, and can do 10 Gbe on paper. But they top out at 7 Gbps on Macs, which don't implement the USBx2 spec.
YMMV - I have three RTL8156 2.5G dongles - one in my Synology NAS, and two in different spots where I usually sit down in a chair and plug in my M1 Pro or iPhone to charge (on USB-C charger hubs) and have never had any issues where they drop out from throughput - at once point I had it running full bore overnight. They're from Cable Matters (2025) and Planex (2024). The only issues I have is sometimes they just don't show up when I connect and I have to disconnect and reconnect. That could also just be an issue with USB-C hubs.
I’m in the process of gradually upgrading an in-house video production studio with <10 seats from 10G to 25/100G. There were attempts to do this years ago, and I found some unused Atto 40G Thunderlink adapters and Sonnet’s 25G adapters. The 40G Attos are EOL, and I couldn’t get the Sonnets to work. The SFP jungle/support/information is really maddening.
Atto’s new 100G Thunderlinks work well. I’ve seen speeds of just over 5 gigabytes per second. Atto definitely does a lot of kernel extension wizardry to get macOS to achieve these speeds.
A bit OT: I hope Blackmagic really shakes up the 100G connectivity market, and that Apple realizes their platform is extremely well-suited for IP Video 2110 workflows — if they can ever get networking under control.
I wonder if similar results would come from just adding a second 10 Gb NIC. If his workload runs SMB multichannel at sufficient queue depth, the load should spread across the multiple paths. If the queue depth is always 1, SMB multichannel is not helping on the 25 Gb NIC either.
> I have SMB multichannel enabled, but this real-world speed limitation could also be related to my use of my lower-power Arm NAS (running on Ampere Altra, with 32 fairly-slow CPU cores).
Based on my own testing with a 25 Gb NIC setup on macOS I strongly suspect the issue is not on the NAS side, and the hardware I was working with is by no means underpowered.
The Mac I was working with is one of those rack mount M2 Mac Pros with a 25 Gb PCI-e card. On the NAS side it was a several hundred terabyte all NVMe flash multi-node cluster, each node with Xeon CPUs and 2x 25 Gb bonded NICs. Doing some rough throughput testing from macOS over multi-channel SMB yields throughput rates that are barely faster than the built-in 10 Gb copper NICs on the Mac.
Using iperf I can confirm that I can get near enough to 25 Gb/s raw network throughput on the Mac. And other non-macOS systems see significantly faster throughput to the same NAS. I am not sure exactly what the issue is that causes 25 Gb NICs to underperform so significantly for file sharing tasks, but I am reasonably certain that the issue is in macOS.
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[ 1.6 ms ] story [ 21.3 ms ] threadSo for instance you have two or more machines that have USB 4 ports at 20 to 80 Gbps and you plug in the appropriate USB C cables to connect them.
What do you need to make the connections appear as a (point to point) part of a regular TCP/IP network? Seems much cheaper than Ethernet if you already have the ports.
Author talks about 4k video, but AI tells me that for "4K production mastering (ProRes 422 HQ, 4:2:2, 10-bit)" the rate is under 2Gbps.
I'm not saying it's not needed, - just curious.
> this real-world speed limitation could also be related to my use of my lower-power Arm NAS (running on Ampere Altra, with 32 fairly-slow CPU cores). I was testing writing to an array of fast enterprise NVMe SSDs, so they shouldn't be the bottleneck here.
He was only getting 1 Gigabyte of throughput out of the built in 10 Gigabit Ethernet connection and moving to the 25 Gigabit connection only made a marginal impact on throughput, after all.
The upside, though, was that I plugged it in, got my throughput, and never had to worry ever again. Remember that engineering time is mucho $$. So troubleshooting overheating, divising a solution, manufacturing it, etc, that all eats into the savings.
The $400 dock would be cool though. It seems smaller than the sonnet and fixes my charging problem. Weirdly I didn't think I'd care about not including transceivers but they did actually come in handy, so that is a downside. Might try to get one of these if I need another one in the future.
Nothing against Jeff Geerling and I love his YouTube channel and I'm glad he's one of us HNer but this crop of circular "I make YouTube vids about big tx speeds and big NAS because I make vids hence I need big tx speeds and big NAS so I can speak about big tx speeds and big NAS because I make YouTube vids about big tx speeds and big NAS" videos is a bit tiring IMO.
I'm not into cryptocurrencies but, I don't know, host a full Ethereum node, host a Plex/Jellyfin server serving thousands of movies, host LLMs, etc.
I mean: talk about something else than editing vids because you make vids about vids.
Plugable 2.5G USB-C to ethernet adapter (bought November 2025), SABRENT USB C to 2.5Gbps ethernet adapter (bought October 2024), UGREEN USB C 2.5G ethernet adapter (also October 2024). In my experience they immediately fall on their face in a speedtest and drop to a couple hundred Mbps, experience packet loss, etc. This is testing across a few modern Apple Silicon Macs.
I now have a WavLink WL-NWU341G 5Gbps dongle with the RTL-8157 that seems to work well, but I've only run a couple of tests-- I am away from my home setup and don't have wired ethernet run to all the rooms where I'm living.
If you do some Googling, there's some good information out there about it, but when I bought the bad ones, I couldn't find any information corroborating my experience.
For my Macs, the IOCrest USB4 adapters with the AQC113 chipset have been rock-solid and can saturate my 10Gbe network. They do run hot but no stability issues. That's what I use and recommend.
The newer RTL8159 based dongles are smaller, cheaper, cooler, and can do 10 Gbe on paper. But they top out at 7 Gbps on Macs, which don't implement the USBx2 spec.
Atto’s new 100G Thunderlinks work well. I’ve seen speeds of just over 5 gigabytes per second. Atto definitely does a lot of kernel extension wizardry to get macOS to achieve these speeds.
A bit OT: I hope Blackmagic really shakes up the 100G connectivity market, and that Apple realizes their platform is extremely well-suited for IP Video 2110 workflows — if they can ever get networking under control.
> I have SMB multichannel enabled, but this real-world speed limitation could also be related to my use of my lower-power Arm NAS (running on Ampere Altra, with 32 fairly-slow CPU cores).
Based on my own testing with a 25 Gb NIC setup on macOS I strongly suspect the issue is not on the NAS side, and the hardware I was working with is by no means underpowered.
The Mac I was working with is one of those rack mount M2 Mac Pros with a 25 Gb PCI-e card. On the NAS side it was a several hundred terabyte all NVMe flash multi-node cluster, each node with Xeon CPUs and 2x 25 Gb bonded NICs. Doing some rough throughput testing from macOS over multi-channel SMB yields throughput rates that are barely faster than the built-in 10 Gb copper NICs on the Mac.
Using iperf I can confirm that I can get near enough to 25 Gb/s raw network throughput on the Mac. And other non-macOS systems see significantly faster throughput to the same NAS. I am not sure exactly what the issue is that causes 25 Gb NICs to underperform so significantly for file sharing tasks, but I am reasonably certain that the issue is in macOS.