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.

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areoform an hour ago | parent | next [-]

https://developer.apple.com/documentation/technotes/tn3205-l...

MacOS has supported RDMA over thunderbolt since March 19th.

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wrs an hour ago | parent | next [-]

That is just RDMA itself and seems to be aimed directly at distributed inference (no surprise there!). Now they need to update the SMB driver to make use of it.

	▲	geerlingguy 32 minutes ago \| parent [-]
		Yeah, raw RDMA is one thing, making sure other protocols can use it is another... hopefully Apple gets there, but right now SMB with RDMA is probably a tiny, tiny niche. I do wonder what Apple's custom-built servers are running for networking. I wish they still made Mac Pro-level chassis specifically for better IO. Thunderbolt 5 is nice, but far inferior to a PCIe x16 slot (which can hit 400 Gbps networking) nowadays.

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dlcarrier 43 minutes ago | parent | prev [-]

Is RDMA something worth looking into for connecting two random Linux computers? I've been extremely underwhelmed by the stability and performance of my NFS shares.

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olavgg 33 minutes ago | parent | next [-]

Yes, nfs with rdma will increase your performance significantly.

	▲	gorkish 23 minutes ago \| parent [-]
		If your storage devices are native PCIe and your network is actually fast enough and your nics and switches have the proper hardware and driver support and your switches are properly configured and your nfs client and server configurations are tweaked just so, and you hold your face in just the right position The perf is amazing

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esseph 29 minutes ago | parent | prev [-]

NFS 4.1 / 4.2?

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gorkish 27 minutes ago | parent | prev | next [-]

This is a ConnextX4 on a thunderbolt bridge. This is well trodden territory. Unless some hero of open source has come to bat recently, MacOS doesn't support RDMA with this card or over Ethernet at all for that matter. It's only supported over Thunderbolt.

His iperf3 results show that it's able to go full beans on a single 25g port. A cross platform SMB file copy is kind of a meaningless benchmark in this context.

IMO a pretty cool product would be a network switch providing native thunderbolt interfaces to multiple upstream hosts. That wouldn't magically fix this RDMA issue, though. This is just a separate thought. Seems like the kind of thing Mikrotik should make.

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cyberax 22 minutes ago | parent | prev [-]

I have a 25GbE setup using Thunderbolt, kinda similar to the author's. Except that my fan is held together by a piece of string, not a 3D-printed enclosure.

I found that SMB on macOS is just bad. If I try to heavily load it (e.g. by doing mass conversions in my Audible library), it can cause stalls and disconnections.

I managed to find a set of parameters (in /etc/nsmbd.conf) that makes it work more-or-less reliably by trial-and-error: dir_cache_off=yes, file_ids_off=yes, notify_off=yes, mc_on=no.

It's still terrible, though. It's so bad that Linux in a Parallels VM works _better_.