Hi and thanks for the report, I have tested my RockPro64 with a Mellanox 10GbE card and came to similar conclusions, while you can use the network bandwidth, you need a multi-threaded/high performance server process as well, otherwise you will get limited by the single core A72 throughput.... 330MB/s linear doesnt sound too bad, with the theoretical limit for the USB3/UAS SATA stuff being 390MB/s...
Come have a chat in the Pine IRC channel >>