SCSI Element AddressingEvery logical library starts at the first drive slot with the current assigned elementstart address (default value 256). It will be incremented from the bottom to the topslots for every drive slot. There is one exception to this addressing scheme toaccommodate libraries currently in the field. A 4U library which contains only fullheight drives will continue to have the addresses assignments 256 and 257, thuscausing no interruptions to their operation. Drive slots will still be incremented by1 for each drive slot position.Note: Exchanging drives with different form factors will result in the libraryneeding to be reconfigured.The SCSI specification does not allow gaps in the SCSI element addressing. Specialhandling is needed for empty drive slots to fulfill the specification. Also driveswhich are temporarily removed need to have their address preserved to notconfuse the attached host and host application. Generally only drives are reportedwhich are currently physically available or temporarily removed. Empty (unused)slots which are located at the bottom or the top should not be reported, with anexception in case of a “removed” condition. A drive slot which does not contain adrive and has a position between used slots needs to be reported as a SCSIelement. To signal the host application that this slot is not usable, its ACCESS bitwill be disabled.a77ug164Drive 3256Element AddressDrive 2256Element AddressDrive 1256Element AddressMagazine1Magazine2Magazine3Magazine4Front sideDrive 4256Element AddressFigure A-4. Configuration of a Four Partition SystemSCSI Element Slot4321SCSI Element Slot43212572562572562584U Unit with only FH drives(1 logical library)4U Unit with FH and HH drives(1 logical library)a77ug165Figure A-5. Examples of SCSI Element AddressingAppendix A. SCSI Element Types and Addresses A-5
