Why is FTP limited to 2 MB/s between Debian 13 and Unraid?

Check the hardware and storage path of the emulation machine as well. A small single-board computer, an SD card, or a slow filesystem could become the bottleneck, although 2 MB/s would still be unusually low for a gigabit connection. In this case the machine has a Ryzen 7 5800, an RTX 3060, and 16 GB of RAM, so the hardware itself is unlikely to explain the speed. Since accessing the share directly is much faster, the issue is more likely specific to the FTP service, client, or transfer settings.

FTP is an unusual choice for a modern file transfer, so it may be worth testing another protocol such as SMB, NFS, or SFTP. That said, FTP can still work fine; the useful comparison is whether another FTP client or a command-line transfer performs better than FileZilla. The main reason for using FTP here is convenience, since it makes moving files easier without needing to operate the target machine directly.

Start by testing the actual network connection with iperf3 on both systems. A healthy gigabit link should usually report roughly 940 Mb/s in each direction. If the iperf3 results are normal, the problem is probably higher up the stack—such as FTP settings, the client, filesystem behavior, or packet retransmissions. A packet capture with Wireshark could help identify negotiation or transmission problems.