FC Architecture

FC Fabric
  └── HBA Driver (lpfc / qla2xxx)
        └── SCSI Mid-Layer
              └── SCSI Disk (sdX — one per path)
                    └── dm-multipath
                          └── /dev/mapper/mpathX  ← application uses this
                                └── LVM (optional)

• Each FC path presents as an independent sdX device in the kernel.
• dm-multipath aggregates all sdX devices for the same LUN into a single /dev/mapper/mpathX.
• Applications and LVM should always target the /dev/mapper/ device, never a raw sdX.
• ALUA (Asymmetric Logical Unit Access) indicates which paths are preferred (active/optimized) and which are available but non-preferred (active/non-optimized).