This read-only integer is the physical device number within its Hot Swap module, forming the second part of the composite index into hpnsaHSDevTable alongside hpnsaHSDevModuleIndex. An admin uses it to identify a specific drive bay position when checking whether that bay's device is present, connected, and addressed correctly. For example, hpnsaHSDevIndex 3 would refer to the fourth physical bay in the cage identified by the corresponding module index.