In Progress CPANEL-43121 - File downloads from cPanel's File Manager are weirdly slow

[spaceman]

For reasons unknown, downloading files from cPanel's File Manager is weirdly slow, or highly variable in download speed, like they're being throttled.

I've proved this across a number of servers, running different OS's and cPanel versions, and also with a 3rd party systems administrator.

To test this for yourself, upload a large file (suggest > 500Mb) to a public_html folder, and test by downloading this file directly from the website, e.g. www.domain.com/largefile.txt

Then login to cPanel for this account, navigate to File Manager, find the file in the public_html directory, and click 'download'.

Big difference, right?

If this is NOT your experience, I'd like to know!

 

[cPRex]

Hey there! cPanel doesn't impose any type of ratelimiting on the system in any area, so it's definitely odd that you're seeing this. Unfortunately I don't have a good explanation. They do use different protocols, so I'm not surprised it's different, but it shouldn't be vastly different. How different were the speeds you were seeing?

 

[spaceman]

1Gb file download speed test

Radically different.

If you don't mind downloading a 45MB video file, click on the above link.

Up to 1m8secs that's me downloading a file called "1GB (1).test" via the web browser from File Manager - mostly super slow, up and down occasionally.

Then you'll also see the identical file being downloaded as "1GB (2).test" direct from the website (LiteSpeed). Massively faster.

Even when "1GB (2).test" finishes downloading, it doesn't help to speed up the download of "1GB (1).test"

I'm very keen to get to the bottom of this

 

[cPRex]

What if you try with a smaller file, such as something in the 50M range? Do you see the same difference?

 

[spaceman]

Same issue, regardless of file size being downloaded.

fyi: I created a full cPanel backup of an account today, size: 160Mb.

Downloading it from the web interface took about 5 minutes

Via ftp took 19 seconds.

Advice from cPanel support is to disable "net.ipv4.tcp_tw_reuse" - https://support.cpanel.net/hc/en-us...3-How-to-modify-sysctl-settings?source=search

We've tried the above, but it made no difference. Except that we didn't reboot the server after making the change, so will try that and report back.

 

[cPRex]

I don't think that sysctl change would be related at all.

My thoughts on this are that the cPanel interface uses a customized PHP system to deliver the content. As in, you can completely kill Apache and PHP on the server, and the cPanel and WHM interfaces still continue to function. It wouldn't surprise me at all if your system is hitting the cPanel memory limit, or that we read the files much more slowly to conserve RAM. This would be especially apparent with larger files such as the ones you're working with, but with more "normal" files that are a few megs or less, users will likely not notice.

You could try increasing the RAM allocated to cPanel in WHM >> Tweak Settings under the PHP section and see if that offers an improvement.

 

[spaceman]

Sincerely thanks for that.

The VPS has plenty of spare resources:

- RAM 32Gb, rarely uses more than 16Gb
- 8 x vCPU, rarely uses more than 50%
- Disk space, 525Gb used out of 700Gb

Load averages are typically 2-3.

Max cPanel process memory has been increased in Tweak Settings from 4096 (default) to 8192.
Max cPanel/WHM/Webmail service handlers has been increased in Tweak Settings from 200 (default) to 1,000.

Still no improvement :-/

The truth (solution) is out there - somewhere!

 

[cPRex]

I don't think there is a solution to this one - I think we just secretly ratelimit large downloads to limit cPanel's RAM usage at the expense of speed.

 

[spaceman]

Bizarre!

 

[cPRex]

I've created case CPANEL-43121 for our team to look into this. As people start and use File Manager more than FTP, this is something I would hope we can resolve. I'll let you know if/when I hear an update!

 

[spaceman]

Thanks for this: https://support.cpanel.net/hc/en-us...eeds-are-much-slower-than-using-an-FTP-client