FFS 3x slower than other SFTP client

[ryan101]

I'm transferring large files between an SFTP server at my house and my computer at work. At my house I have a fiber connection with latency in the 1-2ms range and an upload speed of 6.1 MB/s. At work I also have a fiber connection with much more bandwidth than that.

When I connect to my SFTP server using Filezilla at work, I'm able to download a single large file or several files at 6.1 MB/s. However, when I connect to the same server and download the same file using FFS, I get around 1.8 MB/s, never more than 2 MB/s.

I've tried various combinations of connections and channels but with no effect. When I'm syncing several files at once I get the same 1.8MB/s that I get with a single file, thus the additional parallel connections are not able to overcome whatever is limiting my speeds. I also replicated these results with the Filezilla client limited to a single connection.

I'm using version 10.18 donation edition on Windows 10.

Any ideas on why I would be getting stuck at 2 MB/s with FFS but not other software connecting to the same server? Any tests I could run to try and isolate the bottleneck?

[Zenju]

I also replicated these results with the Filezilla client limited to a single connection.

FreeFileSync also supports multiple connection with the Donation Edition: https://freefilesync.org/manual.php?topic=performance