40gbe speed questions

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Joshh

Member
Feb 28, 2017
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Now that 40gbe hardware has fallen a bit in price I made the move but had some questions on the speeds I am getting.

My setup:

R720xd with a ConnectX 3 running ESXI, the VM is Centos connected with a VMNetx3 adapter. On the other side I have an R710 with a ConnectX 3 running ESXI and a Centos VM. Both VMs are connected to a vswitch and the Cx3’s are connected directly via a twinaxe qsfp + cable (no physical switch in the picture… yet.)

Running Iperf I am getting about 1600 MB a sec between the vms.

This might be a dumb question but if I Iperf 127.0.0.1 on the 710 I get about 21gbps. Is that the max I will ever get out of this box? I had assumed there was some offloading of some of the work to the NIC and I guess I assumed I would get better performance.

I did read this thread Can't get more than 20Gbps out of a 40GbE network - Suggestions? but am still not coming close to this formula
Gen 2 x8: 40 GT/s*8b/10b = 32 Gbit/s (4 GB/s).
 

i386

Well-Known Member
Mar 18, 2016
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What exi version?
Connectx-3 vpi or en cards?
Firmware (and drivers) up to date?
Jumbo frames enabled?

I would rerun these tests with linux livecds to eliminate esxi driver problems.
 

Joshh

Member
Feb 28, 2017
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ESXI 6.5, Connectx3 EN, Firmware is up to date but the drivers are the OOTB ESXI 6.5 drivers. Yes Jumbo frames are enabled. Ill try the live cd route this weekend. I was able to double my numbers by moving the Connect X 3 card from the outer most slot to the 8x slot on the center riser. This got me to 2600MB a sec.

Edit* Found this today... Network Improvements in vSphere 6 Boost Performance for 40G NICs - VMware VROOM! Blog

Might help on my quest to 40gbe.
 
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