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I have a fairly simple home network, hardwired with gigabit switches, with a wireless router that generally handles our laptops. I have a situation in which my network - wired AND wireless - becomes saturated when I really don't think it should:

When copying a large, or many small files - on the order of 5GB total - from one of the laptops to the main file server on my network, it will, after just a few seconds, bring the entire network to its knees. A video being streamed from a server across an entirely hardwired path will start to stutter and gasp until the file transfer ends.

The file transfer over wireless maxes out at approximately 2Mbps. Let's assume the video - in this case, a 480p stream, might at most want 1.5Mbps, for a grand total of a whopping 3Mbps load on the network. The wireless laptop on which I write this speedtests out on the big, ugly Internet at over 80 Mbps, and I realize that's a bit of an idealized number. But the broader point is that 80 Mbps of even theoretical available throughput shouldn't be taxed by a 3Mbps load. Yet mine sure seems to be.

Is this indicative of some misconfiguration on my part? Or am I just being a dunderhead and not understanding some basics about how data flows on the network?

EDIT: Per comments below; the only hard server on the network is a box running Ubuntu; it has two gb nics, one to the outside world, one to the inside, and it hosts two VirtualBox VM's. One VM hosts media files played back by small RaspberryPi boxes running OSMC; the other VM is the firewall box. The Ubuntu box is one I built about three years ago; Intel i5-4460, 8GB RAM with a single 2TB WD (ST2000DM001) hard drive

EDIT 2: As a test, I started streaming two HD video streams and both played flawlessly. This would reflect pulling about 3x the data from that VM across the network as in my original scenario. Are we suggesting that data going to (writing) the server while streaming is the problem? VMs are going through taps in a virtual bridge to access the network; if those taps are just implemented as file descriptors, could the two-way flow of data across that single tap be the bottleneck?

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    Sounds like the problem is with your server(s) not your network. What does the internet Speedtest do when you say the network is “stuttering?” Does the internet speed test cause any disruption to the other transfers? I suspect not. This isn’t a network issue, this is a performance problem with your servers. Are they virtual machines? You need to give more details about the hardware and OS. Especially the disk subsystem and virtualization platform.
    – Appleoddity
    Commented Jul 26, 2018 at 23:01
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    Does the hardware path include the router itself? Very often "switch ports" on a router will slow down the connection, because its not a true switch, its multiple ports using software to create a switch - and the CPU in these devices is not great. The solution here is to wire everything to proper switches and only a single port from the gigabit switch to a LAN port on the router.
    – davidgo
    Commented Jul 27, 2018 at 1:17
  • @davidgo If I understand your question correctly, the right answer is "yes" and "no." I only use the wireless router effectively as an access point; the Ubuntu box hosts a VM that actually goes out to the Internet. The Ubuntu box has taps off a virtual bridge, and the VM's connect to the network via the taps. Yeah, its a bit unorthodox, but I didn't want the hard server directly on the net; the "public" IP goes to the firewall's VM.
    – David W
    Commented Jul 27, 2018 at 1:30
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    Guess: Bufferbloat. Some intermediate buffer is filling up after a few seconds, and the full buffer causes drops on all network traffic, instead of just dropping packets for the big transfer (which would cause the big transfer to slow down properly). Cameras have constant framerate, so they are not subject to this.
    – dirkt
    Commented Jul 27, 2018 at 11:17
  • You can rule out the switch by testing it with jperf/iperf on two PC's. (Not the server). I have to agree with the others, this sounds like a problem with your vm-box. Have you considered adding some identical drives to get raid-5 or raid-10 on it? You should get considerably better read/write bandwidth. Are these two gig-e NICs built in? Pci/pci-e cards? What's the make model of them?
    – Tim_Stewart
    Commented Jul 27, 2018 at 13:51

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