Short Version: Enabling FasTrack QoS slows down regular FTP traffic (up or down) from about 800 KB/sec to about 60 KB/sec.
I noticed tonight while trying to upload (or download) a 3 MB file to my web hosting server using FileZilla FTP that it was quite slow – about 66 KB/sec either way. I duplicated the experience in WinSCP so I knew it wasn’t just FileZilla. I then figured out that if I connected via SFTP instead of plain FTP, it was faster – about 800 KB/sec average.
I wondered about my server but also took a look at my router settings in the meantime. Just for kicks, I tried disabling the FasTrack feature and regular FTP sped up to about 1 MB/sec up and down. I re-enabled FasTrack and it slowed back down to 60 KB/sec or so. Disabled it again and it was fast again. So for some reason it seems evident that FasTrack slows down regular FTP (but not SFTP) when enabled.
Why does this happen?
Firmware Version: 1.06.18
Firmware Build Date: Fri 21 Dec 2012