hi raghavendra, I have not done this but think it should be not problem to commingle, as long as you be alert for some QoS gothca's. Im playing with the ISCSI prioritization now and have run into FCoE in the documentation. some of the obstacles would involve making sure you prioritize and queue ISCSI the way you want it. Most nexus have a default 50% BW limit on links when FCoE is enabled. So 50% Ethernet and 50% FCoE.
With ISCSI, running on the same link (i.e. trunk), you may hit that limit and wonder what is going on.
Also, there are some interesting things like QoS-groups on nexus. with 5k, there is a default one for FCoE (qos-group 1) - set up automatically. this follows a priority queue model (not paused, not dropped compared to other traffic). With ISCSI, you probably want to set up another QoS group, like group 5 for example, and match in COS5 and ISCSI protocol. and then define this as a no-drop, priority. in doing this there are a few crazy rule son nexus like cannot have more than 2 priority queues if you have a bunch of other queue defined. this varies based on platform, and needs to be researched. For example on the 7K:
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/4_2/nx-os/qos/configuration/guide/qos_nx-os_book/queuing.html
another gotcha is that your fex model can only support COS classification in class-maps. see this link, and search for 2232:
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/troubleshooting/guide/N5K_Troubleshooting_Guide/n5K_ts_qos.html
there are some special considerations here.
hope that helps. im not an expert at this, and am still researching myself. take a look at this link, where im asking some questions and have detailed my first draft of ISCSI prioritization on N5K:
https://supportforums.cisco.com/discussion/13019351/nexus-n5kn2k-jumboframes-l3-iscsi-qos-priority-queue-no-fcoe-disable
