MDS with Nexus network

[froggerdata7]

I was browsing the INE CCIE Data Center courses and came across the sample video under storage.  The topic is SAN Port Channels.

My question is in the diagram, they show 2 JBODs, connected below it are 2 MDS switches, and below that connected to 2 Nexus 5Ks.  Why would you have the MDS connected to the Nexus?  Won't the servers connect to the Nexus for the LAN, and the storage volumes connect to the MDS for the SAN.  Or is this scenario using fabric interconnect? Or maybe FCoE? 

Just looking for a little clarification on this design, as I'm starting to learn more about data center storage.

[Walter Dey]

Nexus 5k supports classical fibrechannel, FCoE and classical Ethernet.

I have customers, who use N5k as a plain FC switch, or customers, which plan to migrate from classical FC to NFS; with N5k they can recycle their FC ports and use them for NFS.

[froggerdata7]

I know the N5K can be used, but my question is why this design with MDS and N5K?

Here is the design topology from INE lecture video that I'm referring too.

[Walter Dey]

Why ? this is a typical lab (CCIE) ivory tower setup ? It simply implies, that N5k can be used instead of a MDS; although the price tag is of course higher than MDS; and don't forget, MDS and N5k are not 100% feature compatible (regarding classical FC).

Walter.