The impossible 10gb issue

[JohnBee]

I have an unraid server on 10gb network and have been enjoying near full read/write saturation with my workstation(1.1-1.2Gb/s), thanks to a generous nvme cache and a bit of tweaking to mtu.

 

That said, I then decided to add another pc to the mix, but soon discovered that I cannot achieve anywhere near the same write speeds than with my own workstation, and in spite of using the very same NIC and profile between them.

Now one would think this would be a hardware issue(pcie lanes, etc), though a bit of testing revealed the PC in question, to be fully capable of maxing out both read & write to other machines on the network.

Beyond this, I even tried swapping the existing NIC and connection(drop-in), into said PC, only to find the very same limitation at work(350-400MB/s), and after doing 1.2GB/s on the previous machine ...

 

I also tried using a fresh Windows(10) installation, to rule-out any OS related issues, as well as swapping-out different NIC's, to no avail...

 

Thus leading to ask, how is this even possible?

I must admit, this experience has me questioning the very fabric of reality lol

 

I did manage to make some(mediocre) progress with extra directives in smb settings, though nothing to write home about(very minor).

 

Whatever the case, and as I was able to rule out pretty much everything other than smb, the question is, why would this even happen in the first place?

 

How could unraid/smb possibly differ between two pc's, using the same nic, os, processor, nvme and network settings, to the point of limiting write speeds to less than 1/2 the potential speeds?

 

At any rate, I was hoping someone might have some ideas or suggestions in interrogating this further, and moreso, in uncovering an explanation and cause - if not only for my own sanity lol

PS, also wanted to add that I can effectively max-out writing to Unraid server from PC, using sFTP with multi-threaded transfers, and that single threaded transfers are limited to 350-400MB/s 
 

Edited September 12, 2024 by JohnBee

[JorgeB]

Are the speeds better from one PC to the other? Also, did you run an iperf single stream test in both directions?

[JohnBee]

Hi and thanks so much for answering.
That said, and when connected to one another(Win 10 file share), both machines max-out their 10Gbit/s throughput capacity in read & write, to and from one another.

That said, I have not run any iperf tests as of yet, and so if you have any suggestions on how I might do so to interrogate matters further, that would be most helpful also.

Edited September 12, 2024 by JohnBee

[JorgeB]

I would start by running a single stream iperf test in both directions.