Virtual TapeServer SCSI-to-FC Adapter User Manual

C-3
Appendix C: Addressing, Structures, and Operation
Auto Assigned Addressing Option
The Auto Assigned option is similar to the Indexed addressing, but with the distinction that the
table used is created through SCSI device discovery on power up or reset, and not otherwise
retained. As the unit performs device discovery on the SCSI bus, the Index table FCP LUN values
are filled with adjacent FCP LUNs referencing each subsequent SCSI device. The host system will
then detect every attached SCSI device without voids, allowing full device discovery to the host.
This allows easy configuration in environments where SCSI device ordering is not important, and
where hot plugging of SCSI devices will not occur. Tape libraries are excellent candidates for
using Auto Assigned Addressing. Configuration options provide for the SCSI discovery to be
performed in order of bus, target, or LUN as desired for the specific environment.
Indexed Addressing Option
Indexed Addressing allows for host bus adapter (HBA) drivers that only use Peripheral Device
addressing to access SCSI devices attached to the VT5900-SA. This is done by use of a table,
which is indexed by sequential LUN values, indicating selected BUS:TARGET:LUN devices. It is
not possible in this mode to address the VT5900-SA as a controller unit directly. The table has the
structure as shown in Table C-6.
The maximum size of the table is equal to the number of buses times the number of targets per bus,
less one initiator ID per bus, times the number of LUNs per target.
The index table can be manually edited. A method is also provided to perform SCSI device
discovery, and fill the table in the order that SCSI devices are discovered on the SCSI buses.