2 2k8r2 VMs on same host- slow network. different hosts, FAST!

[pchadwic]

Hi all-

troubleshooting a network performance issue.

2 VMs, patched 2k8r2 4cpu, 4gig, no firewall. e1000 nic.

standard switches, 1 uplink nic (1gig).

Testing with iperf -P 4, I get the following-

2 VMs on different hosts, ~920mb/sec (expected).

the same 2 VMs on the same hosts, ~70mb/sec. (very bad).

these are on the same network on the same standard switch.

network between the hosts is 1gig into a newer cisco switch.

any ideas? I'm running hardware version 8, and ESXi version 5.0.0, 821926. (we are unable to run 5.1 at this time)

thanks

[pchadwic]

Additional testing has shown-

2 ubuntu 64bit VMs w/ e1000 nics- different hosts, 920mb/sec

same hosts 4.7gb/sec (which is strange with the 1000bit nics, but whatever)

so it appears to be an issue with the 2 windows VMs on the same vSwitch?

[struijen]

have you tried giving them a static IP, and putting in your own DNS servers?

[pchadwic]

they have a static IP and are in our internal DNS. this isn't a DHCP/resolution issue, its a throughput issue.

[Rubeck]

Hi..

Do you see the same result on Windows when using vmxnet3 vNICs?

..,4.7gb/sec (which is strange with the 1000bit nics, but whatever)

Not really... That would be expected unless the driver running it caps it a 1000Mbit... The vmKernel tries to push data as hard as it can.

/Rubeck