Power and rack-space savings of virtualizing network gear
According to my tests in my datacenter there is no saving and in fact maybe require more rack-space and power. This was with two rows of 12 server racks and 1 network rack each; one set up with traditional networking kit (two datacenter grade top-of-rack 10-Gig and 2 1-gig switches in each rack and 2 many-blade core switch with routing and firewall modules with separate physical IDS/IPS and Load-balancing appliances) and the other row with basic layer-2 switches as specified by the SDN provider and the network rack replaced with a server rack.
Per-watt the traditional switches were far more power efficient per packet end-to-end between VMs and the exterior of the test network than the software-defined network and virtualized appliances. As far as testing for space, I only ended up saving a paltry 10 RU of space in a row of 13 server racks.
Overall, the added management overhead, power, and server usage of SDN cancelled out any benefit when using very basic layer-2 switches and virtualizing everything. I will be sticking with traditional networking and trunking all VLANs to each of the VM hosts and letting the network gear handle the packets.