Windows Guest slow network performance

[mygeeknc]

I just installed a new Windows 2k8 Std server on a 3.2 host that already has a 2k8 guest running on it. The new guest is getting horrible network performance, even to the other guest vm on the machine, to the tune of ~200Kbits/sec where as the existing guest is getting ~500Mbit/sec.

Both adapters are VirtIO and using the same driver and are both stored on the same NAS.

Does anyone have any ideas as to why this VM would get such poor network performance?

 

[tom]

how do you measure the speed?

 

[mygeeknc]

Hey Tom, I used iperf to test the network speed.

 

[tom]

iperf on windows is the wrong tool.

see http://forum.proxmox.com/threads/18189-Windows-network-performance-test-tools

 

[mygeeknc]

This is the result: http://d.pr/i/ACAu

While it does seem better, I would expect much higher throughput from a VM to VM on the same host.

 

[spirit]

What is your host cpu ?


you can check on the host, if you see a vhost-net process. (they are 1vhost-net process by vm network interface).
Then check the cpu usage of theses vhost-net process. (They can't use more than 1core, so 100% is the max of the process).

if they are at 100%, you are cpu limited.

(But I can achieve around 1gbit/s with old xeon).

 

[mygeeknc]

Each host server has 2 Xeon 8 core CPU's.

 

[hotwired007]

What is the physical network hardware? NICs/Switches

Have you tried with the other Virtual Network cards? I always found that the Intel E1000 performed better on my Dell servers with broadcom NICs