I have a Hyper V host on windows server 2012 and a guest virtual machine also Windows server 2012.

I have two NICs..one is assigned to the guest and the other the host.

DNS is fine and external network access is fine from both the host and the guest.

I can FTP from the guest virtual machine to a remote machine at 10mb/sec plus.

I can FTP from the host machine to a remote machine at 10MB/sec.

What I cant do is transfer anything from the guest to host or vice versa, using either FTP or a simple network share at anything over 2mb/sec and its very variable and the speed jumps around all over the place.

I have broadcom NetExtreme II NICs 5716C and I have tried changing the adaptor settings; Virtual Machine Queues enabled/disabled

which had no effect, even after a reboot.

All Hyper V settings are the defaults and the guest has a fixed size virtual HDD.

Anyone have any ideas about where else I can look for whats causing this..?


1 Answer 1


You don't mention which Linux you're using. (In fact, I just have to infer that it's Linux from the FTP and Samba strategies.)

Use an upstream kernel or a very recent kernel from your distribution. The Linux drivers for Hyper-V have improved a lot, and old kernels don't get the benefit.

Lastly, make sure you're using the paravirtual NIC, not the "legacy" NIC, for your VM. The emulator for the old legacy NIC will be a bottleneck.

  • 1
    Thanks for the reply..it's Windows Server 2012..sorry I abbreviated that to just Server 2012. Mar 10, 2016 at 22:08
  • So how does Samba figure in? Mar 12, 2016 at 0:10
  • Sorry brain drain, SMB share...well its CIFS now I guess. I just setup a simple folder share on each Windows Server 2012 to test. Thanks. Mar 12, 2016 at 6:58

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