Jumbo Frames and QoS for iSCSI (on Nexus 5548UP)

[Boudewijn Plomp]

Hi,

We have a FlexPod environment with only iSCSI. We also boot from iSCSI. We want to configure Jumbo Frames (MTU 9000/9216) on our Cisco Nexus 5548UP switces as part of the FlexPod. I have found many white papers, but they don't describe exactly wat we need.

First of all I am looking for a good white paper dat describes how to configure the Nexus 5548UP switces with Jumbo Frames for iSCSI. Also with platnum, gold, silver (for iSCSI) and bronze. I also have two other questions:

- Can you only enable Jumbo Frame switch wide on a Nexus 5548UP?

- Do you need to use QoS?

I hope somebody can advice me on this.

Boudewijn

[Boudewijn Plomp]

After posting my question. I finally found a lot of information and took the change to configure QoS on our Nexus swithces. Although it get QoS working in the right policy-maps for type queuing I can't get Jumbo Frames to work properly. :-(

[Boudewijn Plomp]

We have just succesfully implemented Jumbo Frames (MTU 9000) in our envornment on UCS, Nexus and NetApp. So far we have tested, it shows a big performance improvement.

I must add we had to open a case with Cisco TAC Support because we kept having issues with QoS on the Nexus switches. Although we had configured everything correctly, we finally found there was a very surprising reason for it related to NetApp. Apparently when you configure a trunk port with VLAN tagging on a NetApp filer, all traffic coming from the NetApp is tagged with a CoS value of 4. And it cannot be changed! It took us days to discover this. So be awar of this if you run in simular issues.