Logical units (LUs) that are exported by the HDS USP and NSC report identification descriptors in the vital product data (VPD). Thesystem uses the LUN associated binary type-3 IEEE Registered Extended descriptor to identify the LU.
An LU path must be defined before an LU can be accessed by a host. The LU path relates a host group to a target port and to a set of LUs. Host initiator ports are added to the host group by worldwide port name (WWPN).
The HDS USP and NSC do not use LU groups so all LUs are independent. The LU access model is active-active and does not use preferred access ports. Each LU can be accessed from any target port that is mapped to the LU. Each target port has a unique WWPN and worldwide node name (WWNN). The WWPN matches the WWNN on each port.
The HDS USP and NSC can use any logical device (LDEV) as a Command Device. Command Devices are the target for HDS USP or NSC copy service functions. Therefore, do not export Command Devices to the system.