Multi-initiator Support
SCSI-attached drives support a maximum of two initiators on the same bus.
Fibre-Channel-attached drives support a minimum of two initiators.
The drive supports untagged queuing when operating with multiple initiators. If a
command from one initiator is being processed when a command other than
INQUIRY, REPORT LUNs, REQUEST SENSE, and TEST UNIT READY is received
from a second initiator, the new command is queued. Commands (other than
INQUIRY, REPORT LUNs, REQUEST SENSE, and TEST UNIT READY) from
different initiators are always executed in strict order of receipt. For drives with a
SCSI interface, if the queue is full or disconnect privilege is not granted in the new
command, the drive reports busy status.
The INQUIRY, REPORT LUNs, REQUEST SENSE, and TEST UNIT READY
commands are always processed immediately, irrespective of whether a command
from another initiator is being processed.
The drive maintains sense data for the supported number of initiators. On
Fibre-Channel-attached drives, if an additional initiator connects to the drive, the
drive erases all sense data for the initiator that least recently connected before
processing the command for the new initiator. See “Sense Data Management” on
page 87 for more details of sense data management.
Status Codes
Table 111. Status Codes
Description Value When returned
Good 00h The command completed without problems.
Check Condition 02h A problem occurred during command execution. The
sense data should be examined to determine the nature of
the problem.
Condition Met 04h This status is never returned, since no supported
commands generate this status.
Busy 08h The drive is unable to accept the command at this time.
This status is returned during the power-on sequence or if
there are commands from too many initiators outstanding.
(See “Multi-initiator Support” on page 96.) It is also
returned when commands are issued without Disconnect
Privilege and when another command is in progress.
Intermediate 10h This status is never returned, since Linked commands are
not supported.
Intermediate
Condition met
14h This status is never returned, since no supported
commands generate this status.
Reservation Conflict 18h This status is returned if the drive is reserved for an
initiator other than the one sending the command.
Command Terminated 22h This status is never returned, since the terminate I/O
process message is not supported.
Queue Full 28h This status is never returned, since tagged queuing is not
supported.
96 Ultrium Internal Tape Drive and 3580 Ultrium Tape Drive: SCSI Reference
