Slow network performance with Intel I350 on Dell R730

[MrSpock77]

Hi,

I have a new Dell PowerEdge R730 with a fresh install of ESXi 6.0U1a. I get some terrible I/O-performance on consecutive reads. This happens intermittently. This picture explains it all:

The reads marked in red have a delay of about 800 ms each. This is a gigabit network with low load. There is a huge amount of these delays until the consecutive read is completed.

There is no network traffic during these delays. Compare the timestamps surrounding the green line in the network trace below with the timestamps above. It seems like we are reading from a buffer, but why is it so slow?

Versions:

ESXi 6.0U1a (build 3247720) and ESXi: 5.5.0U3b (build 3248547)

NIC: Intel I350, firmware 17.0.12, igb driver 5.3.1

I have followed the advice in VMware KB: Low virtual network I/O performance with Intel 1Gbps NIC using igb driver, but that does not help.

This problem does not occur on my other servers (R710, ESXi 5.5, Broadcom NIC).

Any help would be appreciated. I am running out of ideas.

Johan

[MrSpock77]

I think I have made some progress now. The performance seems to be very sensitive to the "Power Options" in Windows. The intermittent delays disappear when moving from "Balanced" to "Performance".

This hasn't been a problem on the other VMs. They have all been on "balanced" for years with no visible impact. I changed one of them to "power saver", and that did actually affect the network performance in a similar way.

Johan