NPIV is fully supported for xVM. The xm command can associate all block devices from one NPIV port to a guest domain. NPIV identity, specifically the port WWN and node WWN, will migrate between devices on the SAN. NPIV allows zoning and LUN masking to be used with Xen. Zoning and LUN masking are useful tools for access control on a SAN. Soft zoning rather than hard zoning (grouping by switch port) should be used on the switch. Soft zoning groups devices by the HBA's Port WWN. If there is more than one physical SAN, or if the system uses hard zoning, the administrator must ensure that the physical HBA is connected to the correct SAN. Switch administrative tools can be used for this purpose.