Hyper-V: What Causes Slow Network Speeds?

Question

Hyper-V

There is a Windows Server 2008 r2 with the Hyper-V role in which there are 5 virtual machines with the same operating system.
The host has two network adapters:
Built-in Intel(R) 82579V Gigabit Network Connection
Optional: Intel(R) PRO/1000 PT Server Adapter
Performed speed testing with iperf between VM-VM and VM-Host.
The results are as follows: If the adapter is free (that is, without a virtual network) - the speed between VM-Host on this adapter reaches 600 Mbps, as soon as you assign it to a virtual network, then the speed on it drops to 30 Mbps. The indicators are the same (+ - 5-10 Mbps) for both adapters.
Google suggested that you need to turn off the TCP Checksum Offload (IPv4) in the adapter settings, but this did not help on any of the adapters.
What else can slow down the network so much?

Answer 1

Cut off VMQ on network interfaces
First, see if the Get-NetAdapterVMQ command is enabled on the VMQ network connections.
If yes, then turn it off with the Get-NetAdapter|Disable-NetAdapterVMQ command
.

Answer 2

And why did you decide that only the network slows down, what about the disk load on the host?

Answer 3

And what is running on virtual machines?

Answer 4

No one else has any ideas?