There are a number of columns on the setup window listing drive SCSI, BUS number, and one listing LUN .
LUN (Logical Unit Number)
=========================
This column identifies the Logical Unit Number of the device on the bus. For SCSI this could range from 0 - 16. This column is undefined for IDE since IDE does not implement LUNs.
In SCSI each target ID may have 8 logical units which are LUNs. The range of SCSI target ids is 0-7 for all SCSI busses implemented in Macintosh hardware today. If a user has a third-party SCSI card installed which implements 'Wide SCSI' then the target ID range can be from 0 to 16.
Article Change History:
21 Jun 1995 - Reworded for clarification
20 Jun 1995 - Corrected minor typo.
Support Information Services