NPIV enables a single FC HBA port to register several unique WWNs with the fabric, each of which can be assigned to an individual virtual machine.
SAN objects, such as switches, HBAs, storage devices, or virtual machines can be assigned World Wide Name (WWN) identifiers. WWNs uniquely identify such objects in the Fibre Channel fabric.
When virtual machines have WWN assignments, they use them for all RDM traffic. The LUNs pointed to by any of the RDMs on the virtual machine must not be masked against its WWNs. When virtual machines do not have WWN assignments, they access storage LUNs with the WWNs of their host’s physical HBAs. By using NPIV, a SAN administrator can monitor and route storage access per a virtual machine.
When a virtual machine has a WWN assigned to it, the virtual machine’s configuration file (.vmx) is updated to include a WWN pair. The WWN pair consists of a World Wide Port Name (WWPN) and a World Wide Node Name (WWNN). When that virtual machine is powered on, the VMkernel instantiates a virtual port (VPORT) on the physical HBA which is used to access the LUN. The VPORT is a virtual HBA that appears to the FC fabric as a physical HBA. The VPORT has its own unique identifier, the WWN pair that was assigned to the virtual machine.
Each VPORT is specific to the virtual machine. The VPORT is destroyed on the host and it no longer appears to the FC fabric when the virtual machine is powered off. When a virtual machine is migrated from one host to another, the VPORT closes on the first host and opens on the destination host.
If NPIV is enabled, WWN pairs (WWPN & WWNN) are specified for each virtual machine at creation time. When a virtual machine using NPIV is powered on, it uses each of these WWN pairs in sequence to discover an access path to the storage. The number of VPORTs that are instantiated equals the number of physical HBAs present on the host. A VPORT is created on each physical HBA that a physical path is found on. Each physical path determines the virtual path that is used to access the LUN. HBAs that are not NPIV-aware are skipped in this discovery process because VPORTs cannot be instantiated on them.
