Troubleshooting 10 Gigabit Ethernet Performance Issues on Windows with Intel E610-XT2 NIC

Initial Network Performance Issues

A user experienced significantly degraded performance on a newly configured 10 Gigabit Ethernet (10GbE) network, with file transfers operating at 100-300 Megabits per second (Mbps) instead of the expected 10 Gigabits per second (Gbps). The network setup included a Windows desktop with an Intel E610-XT2 10GbE card, a UniFi UNAS Pro 8 NAS, and a Minisforum MS-01 miniPC, all connected via 10GbE.

Troubleshooting Steps and Isolation

Initial troubleshooting efforts focused on the NAS, including its RAID 6 configuration, NVMe SSD cache, and running services like Immich. Disabling the SSD cache and stopping Immich did not resolve the performance bottleneck. Further investigation using `iostat` confirmed that the disks were not saturated, and checks on SMB signing and Windows Defender network scanning also yielded no improvements.

The problem was isolated by running `iperf3` directly between the Windows desktop and the MS-01 miniPC, bypassing the NAS. This test revealed asymmetrical performance, with transmit speeds around 133 Mbps and receive speeds around 1.33 Gbps, indicating a client-side issue with the Windows desktop or its network interface card (NIC).

Identifying and Resolving Packet Discards

Examination of the Intel E610-XT2 adapter statistics using `Get-NetAdapterStatistics` showed a high number of `ReceivedDiscardedPackets`. During a 10-second `iperf3` test, this counter increased by 268. The root cause was identified as insufficient receive buffers on the Intel E610-XT2 driver, which were set to the default of 512.

Increasing the `Receive Buffers` property to 4096 using `Set-NetAdapterAdvancedProperty` eliminated the discarded packets and significantly improved receive throughput from 1.33 Gbps to 5.15 Gbps. The transmit direction, however, remained slow at approximately 313 Mbps, indicating another issue.

Further Optimization for Transmit Performance

The next step in troubleshooting the remaining transmit performance issue involved disabling Large Send Offload (LSO) V2 for IPv4. This adjustment was made using `Set-NetAdapterAdvancedProperty` to address the persistent low transmit speeds, aiming to further optimize the network adapter's performance.