PCIe NIC performance lags behind the board-level LAN.
PCIe NIC performance lags behind the board-level LAN.
I just received a 3 gigabit internet connection from my ISP. After checking the speeds, I noticed one of the PCs connected to 10GbE has very slow upload (around 500-800 Mbps). When transferring files locally, it reached about 3.3 Gbps, which is puzzling. I also tested over the local network and with a live Ubuntu USB, but it didn’t work on the internet. I swapped the NICs—using an X520-2 SFP+ with a DAC cable on an Aruba switch—and it still didn’t fix the issue. On the other end, the working PC has a 2.5GbE LAN port and reports 2.5 Gbps, while the non-working PC has a 1.49GbE port and the same problem. Both systems have the same NIC model (X520-2) and similar cables, but only the working one seems to function properly.
I've attempted to reinstall drivers, changed network cards, and swapped cables, yet the issue persists. Another PC performs normally, while this one achieves around 3.5gbps over LAN but struggles with the internet connection somehow...
You restored the original drivers from the manufacturer’s site, avoiding fake scanning tools. I’d probably use SFC/DSIM and consider a clean install via a spare drive. It seems there might be an issue with the PCIe connections, which is unusual since the download happens only online.
Checked the official Intel website. Used a live Ubuntu USB to fix issues with Windows, but faced similar problems. Tested PCIe lanes with PCIE2.0x8 and 3.0x4 NICs—both encountered the same issue. It's strange since locally it runs much better. Switched ports multiple times without success.
The main concern is whether it really matters. Speed tests are essentially the only platforms without upload speed limits. Almost every other site restricts speeds lower than your test outcome. Eventually, the pursuit of an issue with no actual effect becomes pointless.
That is the actual answer but on the flip side, the alternative one functions well and it's surprising. I quietly appreciate dealing with edge cases.
There are several issues with my boxes, particularly on Windows and NFS shares, during uploads. Usually I experience smooth speeds using iperf3, indicating the network stack is working well, but performance to my NAS tends to be inconsistent. I can transfer files quickly between drives at high speeds, yet over the network it slows down unpredictably. Recently, a large file hit a 2.5Gbit limit, and even two identical files on the same drives didn’t reach Gigabit speeds. I suspect the first file was smaller and already in RAM cache, while NVMe transfers behave strangely over the internet. At this stage, it’s still faster than my broadband connection.