Network Speed Veries Significantly Depending on Copy Direction

Hi, I have two Windows 11 computers that are connected to a 10GbE network switch. They both have Mellanox 10GbE fiber connections to the switch. The problem is that when I transfer a large (6Gig) file from Computer 1 to Computer 2, I get around 1,000Mb/s. But when I transfer the same file back in the other direction from Computer 2 to Computer 1, I only get around 118 Mb/s. I am using the same NVME drives on each computer for the copies in both directions. I have made this test multiple times and even tried using different drives on each computer and I get the same results. Something is not right. Any help would be appreciated.

On the second computer, it's on ?


And PCIe Gen 4 ?

Maybe this tweak will help.

If you faced any slowness while accessing files and folders from the network shared drive which mapped to your computer in Windows, then this video contains instructions to resolve the problem of the slow access to network drives in Windows 10 or Windows 11.

I checked the write cache for the drives on both computers that I was using, It would not allow me to turn on write caching. I got a message saying that the device does not allow its write caching settings to be changed. I was copying from an Intel P5800X on Computer 1 to an Intel P5800X on Computer 2. There was still the large copy speed difference from Computer 2 to Computer 1.

For the two drives, they are rated at 6,100MB/s write speed. The 10Gbe should max out at about 1,000MB/s accounting for overhead and handshaking. So that should cap the speed, and I am getting about right about that speed going from Computer 1 to 2, but only 1/10th of that speed copying in the other direction.

One difference between the two computers is that I have a 10GbE ConnectX-6 card on Computer 1 and a 10GbE ConnectX-5 card on computer 2. Could the connectX-6 card be the difference in sending files faster? It does not seem like it should make that much difference, but it is supposed to offload some work from the cpu to the card that connectX-5 might not be doing.

I will make the registry changes from the video and let you know how that turns out.

Check if Jumbo Frame support or TCP offload is enabled in both network interfaces. Open Device Manager, and look at each NIC's driver properties.

A real pain in kiester for me that affects network performance has been virtual drivers from Hyper-V. In particular, if Hyper-V switch manager has an External switch created. I had to resort to dedicating a specific NIC to Hyper-V to prevent drastic performance hits.