What distinguishes an HP switch with a CLOS fabric from an HP switch with a crossbar fabric?

A.
The CLOS fabric can integrate with a virtual switch, which is deployed in a virtualized server.

B.
The CLOS fabric is a requirement for an Intelligent Resilient Framework (IRF) virtual switch with more than
two members.

C.
The CLOS fabric can dynamically shut down power to unused switch ports, proving better energy efficiency.

D.
The CLOS fabric can dynamically load-balance internal traffic over many paths, helping the switch support
40G/100G.

Explanation:
In a modern Clos topology, every lower-tier switch is connected to each of the top-tier switches in a full-mesh
topology. If there isn’t any oversubscription taking place between the lower-tier switches and their uplinks, then
a non-blocking architecture can be achieved. The advantage of the Clos network is you can use a set of
identical and inexpensive devices to create the tree and gain high performance and resilience that would
otherwise cost must more to construct. To prevent any one uplink path from being chosen, the path is randomly
chosen so that the traffic load is evenly distributed between the top-tier switches. If one of the top tier switches
were to fail, it only slightly degrades performance through the data center.
Clos Networks: What’s Old Is New Again, What goes around, comes around – Clos Networks are
back
http://www.networkworld.com/article/2226122/cisco-subnet/clos-networks–what-s-old-is-new-again.html