none
Hyper-V Network Slow RRS feed

  • Question

  • A windows 2012 server standard with a pair of Broadcom NICs.

    I've disabled Virtual Machine Queues and Large Send Offload on the adapter that's serving as the virtual switch but I'm still getting speeds that are 1/5th to 1/10th my normal network speeds.

    The guest VMs are running Debian and CentOS Linux, and are managing enough speed to work with (500-700 Kbps) on random file transfers or remote connections, but are running much slower than the same tasks with any physical machine on the same network.

    Any advice on other possible solutions would be great.

    Thanks.

    • Moved by BrianEhMVP Wednesday, April 23, 2014 3:33 PM moving in case there is a Linux specific issue
    Wednesday, April 23, 2014 1:52 PM

Answers

  • Hello everyone,

    About this issue, have we verified the NIC drivers are updated on the host? I have seen previous cases where this may be the issue. Also, if we need to investigate this further, may I suggest we get a case opened?

    Thanks!
    Patrick [MSFT]

    • Marked as answer by PDS_ Thursday, May 1, 2014 3:28 PM
    Monday, April 28, 2014 10:35 PM

All replies

  • If it helps, the VMs on the same virtual switch do maintain a network speed closer to 9-10 MB/s.
    Wednesday, April 23, 2014 7:46 PM
  • So we have full information to help:

    1)  Which specific versions of CentOS and Debian are you running?  Per the documentation here, are Hyper-V Linux Integration Services built-in, or separately installed if needed?

    2)  A just to confirm the obvious, you have your Hyper-V virtual machine configured with a "Network Adapter", and not a "Legacy Network Adapter"?


    Michael Kelley, Lead Program Manager, Open Source Technology Center

    Wednesday, April 23, 2014 7:53 PM
    Moderator
  • The versions are Debian Wheezy (7.4) and CentOS 6.5. Both should  have the Hyper-V integration services built in according to the documentation. 

    Running lsmod shows that both have the hv_utils, hv_storvsc, hv_netvsc, and hv_vmbus in the kernel.

    They're both using the Network Adapter and not the Legacy version.
    Wednesday, April 23, 2014 8:34 PM
  • Hi, Could you please also check if the behavior is the same for Windows virtual machines? That would help us identify if the problem is with Linux virtual machines or the Hyper-V switch. Please let us know.

    Thanks,

    Abhishek

    Friday, April 25, 2014 3:05 AM
  • Using a Windows 8.1 VM as a test and it also had degraded performance, performing a touch faster than the Linux machines but still barely 1 Mbps. 
    Friday, April 25, 2014 6:30 AM
  • Hi again, One other question. What is the situation with host to host performance? If you are testing these virtual machines on two different Windows servers, do you see the same low network performance between the two servers without using virtual machines? Please let me know.

    Thanks,

    Abhishek

    Friday, April 25, 2014 1:45 PM
  • The host (Server 2012) using the NIC not set as a virtual switch manages to show a performance around 9-11 MB/s so seems to be doing just fine. 

    I've tried connecting the VMs to a few other servers and they're showing the same degraded performance across all their connections. The only ones that don't degrade are when it's two VMs connecting to each other on the same virtual switch.

    Friday, April 25, 2014 7:11 PM
  • Hi, I would also like to know the workload you are using to test the speed. Typically network performance is measured by iperf. What workload are you using to realize < 1MB/s?

    If you are using file transfer then it could be that the dynamic VHDX you are writing to has become the bottleneck. Please could you let me know your workload?

    Thanks,

    Abhishek



    Monday, April 28, 2014 10:17 PM
  • Hello everyone,

    About this issue, have we verified the NIC drivers are updated on the host? I have seen previous cases where this may be the issue. Also, if we need to investigate this further, may I suggest we get a case opened?

    Thanks!
    Patrick [MSFT]

    • Marked as answer by PDS_ Thursday, May 1, 2014 3:28 PM
    Monday, April 28, 2014 10:35 PM
  • Running the driver updates did the trick, it looks like it was a combination of them and some issues with the physical switch that the server was connected to.

    Thanks for the help.

    • Edited by PDS_ Thursday, May 1, 2014 3:30 PM
    Thursday, May 1, 2014 3:28 PM