There are better alternatives
We looked at the Nexus architecture. All I can say is wow. It takes cost and management complexity to a new level. Here's what we saw:
1) Top-of-rack switches, 2) Middle-of-row switches, 3) End-of-row switches, 4) Virtual switches (the Nexus 1000), and, to make it all work, 5) Intelligent cards in the servers (CNA's).
That's FIVE layers of management. And five layers of gear and software to buy and support.
Xsigo offers a simpler alternative. The Xsigo I/O Director replaces the top of rack switches, so there are no additional layers. It works with the existing LAN and SAN, so everything stays the same there. And it manages the I/O in the server plus the external hardware from one screen. Xsigo is an integrated approach that removes cost and complexity rather than adding it.