Turn flow control on for SLES 11?

We are trying to get flow control turned on for our SLES 11 servers to improve our iSCSI connectivity to our storage arrays. We run the ethtool command “ethtool -a eth0 rx on tx on” and have success with rx turning on but tx does not turn on. And we get no error telling us why tx flow control does not turn on.

Does anyone have the correct method for turning on flow control - and making it stay on over reboot cycles - for SLES 11? We are running on ESXi 5.0 and the NICs we are using are E1000s on the VMs.

Any help is appreciated. We are trying to address a high re-transmit rate for our servers running Oracle. When we move them from Dell PowerEdge 1950 IIIs with ESX 4.1 to PE R620s running ESXi 5.0 the re-transmit starts jumping way up.

Thanks much,


A few points:

  1. Switch to using vmxnet 3 adapters in your VM’s. It takes all of 5 minutes in most cases.

  2. Flow control on the emulated NIC is meaningless.

  3. Flow control is not the same as priority queuing. Packets will be processed in FIFO order regardless. So this will not help iSCSI.

  4. You can always create yet another virtual NIC ( using vmxnet of course ) and use it exclusively for iSCSI.

– Bob