The 6500 is a modular core and or distribution (or collapsed core) layer switch designed to handle L3 routing, etc. (because routing is generally done at distribution layer). You probably have a true core layer, requiring more advanced L2.
thank you very much for your answer, but I have a question - do these 2 switch types (6500 vs Nexus) differ in network latency/throughput? I mean, does it provide better performance to use Nexus instead of 6500 switches?
Or maybe when we use 10Gbit NICs from filers to C6503 as single VIF - that is a problem? is there any performance difference between single VIF and multi-mode VIF? (i know that more paths = better throughput, but we barely do more than 1.5Gbit from 10gbit pipe)
and I am trying to understand best network design for my new implementation (based on fas3160 heads)...
I do not have hands on experience with Nexus, just marketing and talking to peers. I think you should call your Cisco/NetApp reps and discuss this. They will surely have a lot more insight.
Regarding your VIF question single or multimode isn't going to matter given what you said about 1.5Gb. From a design perspective I would think there is always an argument to run in multimode. Why spend the dollars on interfaces and not use them.