we need to replace an old NetApp Metrocluster and the compute layer by a FlexPod based infrastructure. The NetApp controllers use FC today. The new FlexPod need to have a Metrocluster config at the NetApp storage layer but we want to move forward using FCoE in order to lower the costs of the FC links between the compute layer and the storage and accross the DC's (note: i'm not talking here about the FC links between the controllers and the diskshelves in this switches Metrocluster config).
The switches we intend to use at the switching layer between the UCS FI's and the NetApp controllers would be NX5596UP which do support FCoE. This configuration is validated for cDOT clusters but i do not find any validation of this setup with a Metrocluster config. The only CVD/NVA i find for Metroclusters using FCoE is using NX7700 series switches with VDC's and OTV.
The problem with the NX5596UP config seems to be the configuration/isolation of the two FC fabrics per DC. However per DC i will have two NX5596UP's and therefore i could define a VSAN-A on the first and a VSAN-B on the second. Would it suffice to connect the respective VSAN's then accross the two DC's (i.e. VSAN-A in DC1 --> VSAN-A in DC2). If so i can use FCoE links (cheaper) between the DC's while maintaining the possibility to interconnect to an existing FC SAN at the NX5596UP level using the UP ports.
Neither of these designs uses the Cisco Nexus 5596, but FCoE configuration is shown in the second link in the Nexus 7000 - Storage VDC section. That should give you a good demonstration how to configure the FCoE on your 5596.
Additionally, we have run a similar configuration to what you're requesting in the data center at Cisco Live, except with a Cisco Nexus 5548 instead of 5596. There are two switches on each site, the switch As are connected together and the switch Bs are connected together. Keep in mind that your max FCoE distance will be lower with the 5K. At Cisco Live, the distance of our fibre between the sites is less than 1km. I believe the max with the Nexus 5K is close to 3km.