I'm transferring files from an Unraid server to a Debian 13 emulation machine using FTP and FileZilla. Both systems are connected over 1 GbE, and the destination is an SSD. Despite that, FTP transfers only reach about 2 MB/s. The same Unraid server can saturate the network when transferring to other machines, and accessing it as a network drive from the Debian machine is much faster. What could be limiting FTP performance on this particular system?
3 Answers
FTP is a pretty dated choice for this. SMB or NFS would probably be a better fit if you’re already accessing the Unraid share as a network drive, and SSH/SFTP is another option if you want a secure file-transfer protocol. The network-drive test being much faster suggests the hardware and basic network connection are probably fine, so comparing the FTP service and its settings against SMB/NFS would be useful.
Check the storage and hardware on the emulation box too. A slow SD card, filesystem issue, CPU bottleneck, or unusual mount configuration could limit writes even when the network is capable of gigabit speeds. However, since the machine has a Ryzen 5800, RTX 3060, 16 GB of RAM, and an SSD, the more likely suspects are the FTP configuration, network protocol behavior, or a problem specific to the destination interface rather than insufficient hardware.
Start by testing the network independently of FTP with iperf3 on both machines. A healthy 1 GbE connection should usually show roughly 940 Mb/s in each direction. If iperf3 is slow, investigate the network path, cables, interface settings, drivers, or duplex negotiation. If it’s fast, then the issue is likely in the FTP server, FileZilla configuration, or the filesystem. A packet capture with Wireshark could also reveal retransmissions or other transfer problems.
I mainly use FTP because it makes moving files to the target machine convenient without needing to use a keyboard and mouse on that system.