Using Jumbo framing

Using jumbo framing can improve performance but if not implemented correctly you can quickly go from poor performance to worse. You first need to make sure the NIC driver supports using jumbo framing. And when deploying you must make sure all devices on the layer 2 side of the network are using jumbo frames otherwise without hitting a layer 3 router which would produce a ICMP “need to fragment but DF bit was set “ message as part of max path discovery you will get very poor performance from that segment of the network.

Smaller frames usually mean more CPU interrupts and more processing overhead for a given data transfer size. Often the per-packet processing overhead sets the limit of TCP performance in the LAN environment. The above graph, from a white paper[2] by Alteon is an often cited study showing an example where jumbo frames provided 50% more throughput with 50% less CPU load than 1500 byte frames.

I'm wondering if you can clear something up for me, how do people tend to configure their 1GbE ports for jumbo frames.

We currently don't have a separate backup network. I don't really want to create a separate backup network right now just to for jumbo frame support although vlans might help with that.

What happens when non jumbo'ed (non netbackup) frames get sent to the jumbo framed ports? From what i have been reading, your network speed will be slower but how much?

Thanks,
Karl