• LUN mapping maps LUNs defined by the storage array into logical units in the HBA:
– LUNs are often associated with volumes
– Structured file systems like VxFS, use VxVM to create logical volumes from multiple LUNs
• The SAN administrator assigns a local OS volume ID to each LUN:
– /dev/dsk/c1t2d0s2 (UNIX) –D: (Windows)
• Mapping survives reboot/reconfiguration
– HPUX and Solaris require Persistent Binding
• Ensures accessibility of storage resources • All HBAs today support LUN mapping
LUN mapping allows administrators to control LUN visibility to hosts: On the subsystem, each logical unit is assigned a unique identifier. The administrator uses storage management tools to assign local OS volume IDs (such as /dev/dsk/c1t2d0s2 or D:\) to specific logical units based on their subsystem IDs.
Persistent Binding controls that storage resources appear consistently to the host.
For example, if a storage device is power-cycled, then volumes on that device may be assigned a different local volume ID by the OS when the volumes come back online. Persistent Binding ensures that the volumes always have the same local volume ID. Persistent binding is typically recommended with disk based assignments on UNIX systems, and is always recommended for tape based assignments on all systems. LUN mapping and persistent binding is typically managed and enforced either by the HBA firmware or by the HBA driver.