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Delay after downloading several small files

Posted: 2019-02-10 21:30
by swbrains
I noticed today when downloading 76 small files (all less than 7 KB, most are 1 KB) from an account on my server that the transfer process starts off pretty fast with the files scrolling by pretty quickly as they are downloaded with no delay between files. But after about after about 50 files or so are downloaded, it slows down and often pauses for about 2-3 seconds, then downloads 2 more, pauses, 2 more, pauses, and so on.

I also see the green activity/download icon in the app go dark during those delays.

Incidentally, I have my FileZilla set to allow 2 simultaneous transfers. If I set it to 5 simultaneous transfers, it will download 5 files, then pause, 5 more, then pause, etc. But the first ~50 files to be downloaded always download with no pauses between them.

I'm using FileZilla 3.40.0 on Windows 10.
I duplicated the issue on my desktop (wired) and laptop (wireless) both using the same current version of FileZilla.
I don't have any third-party firewalls installed on either of my local computer(s) other than the Windows default firewall.
The issue is reproducible every time I download the files.

Finally, I tried installing CyberDuck and under its default settings (it did import the bookmarks from FileZilla), it downloaded the same folder in one continuous stream with no delays, so it seems the server is not causing the delays.

In the FileZilla log excerpt, you can see the commands that are executing when the delay occurs, after the RETR command and before it responds with "150 Accepted data conntection":

2019-02-10 11:31:32 16352 3 Status: Starting download of /public_html/bbs-images/exclamation.gif
2019-02-10 11:31:32 16352 3 Command: PASV
2019-02-10 11:31:32 16352 3 Response: 227 Entering Passive Mode (65,60,11,50,208,97)
2019-02-10 11:31:32 16352 3 Command: RETR exclamation.gif
2019-02-10 11:31:35 16352 2 Response: 150 Accepted data connection
2019-02-10 11:31:35 16352 2 Response: 226-File successfully transferred
2019-02-10 11:31:35 16352 2 Response: 226 0.000 seconds (measured here), 11.96 Mbytes per second

Any ideas why this 3-second delay occurs repeatedly after reaching a certain point in the download queue?


Re: Delay after downloading several small files

Posted: 2019-02-12 08:16
by botg
Are you using FTP over TLS, as indicated by the lock icon in the status bar?

Which FTP server software (product and version) is running on the server machine?