Bandwidth/Speed limitation?

OS is Debian Squeeze, Dell 2950 2 x 4 cores (8 cpus), 16GB RAM. 2 x Broadcom and 2 x Intel Gigabit cards. Dedicated environment. No virtualization.

My bandwidth with the ISP is about 10MB/s (10000 Kb/s). I use a iftop as the util to monitor the bandwidth coming in and out of the server

OS is Debian Squeeze. I did load impact test and found the virtual servers on Virtualmin could not surpass 3MB/s.

I have another web server running under Hyper-V in windows, load impact test on that server hover around 3-4MB/s, and often go to 7MB/s or 10MB/s.

I disabled iptables just to rule out any possibility. It made no difference. The websites under the virtualmin server cannot surpass 3MB/s majority of the time. Sometimes, it could go to 3.4-3.8MB/s, but only for a second, then it drop back down to 2.5 MB/s.

Using another server on a local network, I test upload a file via the Webmin file manager, upload is fast 24MB/s. Then I try downloading the same file, the speed simply could not exceed 4MB/s.

I switched to using Bitvise Tunneling software to do a straight SFTP transfer via SSH. The speed in and out of the server is 175MB/s to 185MB/s. This is straight copying between the two servers on the same local area network.

This rule out one thing. It's not a network driver issue with Debian as it proved to transfer upward of 175-185 MB/s.

I am using Webmin file manage to download the file from the server. Browser is firefox 4.

My question. Why is it so slow to download? Even upload, it supposed to be way up there at 175-185 MB/s. Instead, it hover only at around 24 MB/s? For download, it crawled to no more than 4MB/s.

Downloading is traffic going out of the server. Uploading is traffic coming into the server.

I don't have enought time. But plan to test with cPanel and others to see if I run into the same issue. I also plan to test on a server without virtualmin or webmin installed. But configuring everything manually may prove to be a real pain.

I would love to hear from someone about this issue. Thank you in advance for your help.

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Yeah, it doesn't sound like you're dealing with a limitation of your Linux distribution. Linux doesn't come with any sort of bandwidth throttling enabled by default.

If in some cases you're seeing 175MB/s to 185MB/s on that server, that means there's something else in play that's causing the slowdown you're seeing.

That suggests that something else between your server and desktop is causing that. It could be your hosting provider doing some sort of throttling, or even the ISP where your desktop is located. You may need to contact both your server hosting provider and your ISP to talk to them about your limits, and the throughput you're seeing from your server.

Thanks but here's the scenario.

In my notes, I've explained that after failing to see satisfactory results via the web, we then totally bypassed the internet line. Here's what we did:

1) Have another server (server A) sit on the same local area network as the targeted server (server B). We are not communicating directly between the two servers. No ISP or internet line involved.

2) Use the Webmin file manager. Uploaded a large file from server A to server B. Speed is 24MB/s max. Download a file from server B back to server A is max 4MB/s.

-3) Abandoned Webmin file manager. Instead, we use an SFTP utility like BitVise Tunnelier. Copy a file from server A to server B and vice versa is 175-185 MB/s. We gain this speed every time.

Summary: If what you are saying is true, and the limitation is with the Linux distro, then how would I be able to do this via straight copy... all the time? It seems the problem is with either Virtualmin or Webmin. This slow down only happens when I use the Webmin file manager or have websites services via Virtualmin.

Because the two systems are on the same local area network. My ISP doesn't care what we do between the two servers. We have a Cisco PIX sitting at the gate. It doesn't even wink at what the two servers are doing (non aware). This is simply because we are not even going out of our local area network.

We have another server on the same network, running under Windows IIS, it is serving files just fine at 7MB/s to 10MB/s going over the internet.

The linux distribution is the one I obtained directly from debian.org. You mentioned it doesn't have bandwidth throttling by default. How do I enable it? But then again, I am not sure this is the problem as we can copy files fine using SFTP. Once again, this seems more like an issue with Webmin or Virtualmin.

Your thoughts are much appreciated.

1) Have another server (server A) sit on the same local area network as the targeted server (server B). We are not communicating directly between the two servers. No ISP or internet line involved.

Sure -- and that suggests that your Linux distribution is capable of generating a lot of throughput.

2) Use the Webmin file manager. Uploaded a large file from server A to server B. Speed is 24MB/s max. Download a file from server B back to server A is max 4MB/s.

So is it only the Webmin file manager where you're seeing slower throughput?

It isn't intentionally doing throttling, but it's possible that you're seeing a limitation of a Java-based application.

Summary: If what you are saying is true, and the limitation is with the Linux distro

I want to clarify that I'm not suggesting the limitation is the Linux distro... I'm offering that I don't think the Linux distro is at fault :-)

You mentioned it doesn't have bandwidth throttling by default. How do I enable it?

You can do bandwidth throttling in Linux, but it's a rather complex area. There's a HOWTO regarding it, which is available here:

http://lartc.org/howto/

Andrey,

Thanks very much for your help. You are right, it could be the limitation with the Java-based application. But how about web serving capability. The virtual server created under virtualmin, the max speed I could get out of it via the web is 3-4 /MBs. That figure looks familiar with the outgoing bandwidth I am seeing from the Webmin file manager. For this reason, I have a feeling the limitation is related.

My next endeavor is to install from scratch (PHP5, MySQL, Apache). Then create a website manually. If I get the same issue, then the problem is not with Virtualmin or Webmin. If I get a faster speed, then it is an absolute fact the problem is with Virtualmin or Webmin? This for sure will isolate whether or not the problem is with the application that I am running for such website. Please correct me if I am wrong.

Thanks very much for all of your help. I really appreciate your time and effort.

For regular web serving, Virtualmin just uses Apache which should be able to serve content as fast as your network interface can handle..

Files uploaded or downloaded using the File Manager may be hitting limitations of Java or Virtualmin's built-in webserver, which is much less efficient than Apache.