HP Fibre Channel Mass Storage Adapters Support Guide, February 2007

Chapter 2
Fibre Channel Adapter Installation
Interpreting Hardware Paths
32
LUN Addressing Method Value of LUN field in Fibre Channel hardwarePath.
Peripheral Device Addressing The Target or LUN field of the Logical Unit Number.
Logical Unit Addressing The LUN field of the Logical Unit Number.
Volume Set Addressing
(Flat Space Addressing) Bits 0 - 2 of the Logical Unit Number.
For more information about the fields in the Logical Unit Number, please see the SCSI Architecture Model - 3
(SAM-3) standards document.
Fibre Channel devices can connect to a fabric using either Direct Fabric Attach or Public Loop. Different
devices can have different types of connections to the same fabric; for example, an HBA can have a Direct
Fabric Attach connection to the fabric, while an array has a Public Loop connection to the same fabric.
Public Loop devices have an Arbitrated Loop Physical Address (AL_PA). The AL_PA usually appears in the
least significant byte of the device's N_Port ID. Direct Fabric Attach devices do not have an AL_PA and the
least significant byte of their N_Port ID is usually 0. This is dependent on the switch implementation. Not all
switches adhere to this scheme.
Some switches enable devices in Private Loop mode to connect to a fabric. These switches typically translate
the Private Loop device as either a Public Loop or Direct Fabric Attach device to the rest of the fabric. These
switches also typically translate the rest of the fabric as Private Loop devices to the Private Loop device.