Yes, sure.  Just connect the unused ports to their FC fabrics and zone hosts to them.
Hi , my customer is using a VNX5400 Unified system for Block only. The System is equiped with one iSCSI Module an one FC 4 Port Module per SP. Currently only the iSCSI moduls are used to connect Hosts. First two Ports on the Modules are used for connecting the DM. Is it possible to use the remaining two FC Ports per SP for Block ?  It is not planned for the lifetime of the System to add more DM .   regards Lutz
VNX5400 FC Ports reserved for DM ?