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Using Special Features in Libraries 41
Using Special Features in
Libraries
In a multi-drive library, will more than one automation LUN appear on the
SCSI bus?
In a multi-drive library, the controller in the library is expected to send ACI
commands to switch off the LUN’s visibility of all but the ‘primary’ drive (the
one that supports the automation LUN to which the host sends automation
commands). This allows library controllers to manage their drives and to
achieve a degree of hardware redundancy if the primary drive fails.
New features in ACI 4.1
Asynchronous Notification
This configurable mechanism allows the tape drive to alert the automation
controller asynchronously of important conditions detected by the tape drive.
The drive asserts the ACI_ATN_L line (See page 101) when the drive has
detected one or more of the following conditions:
3
CDB waiting (for Surrogate SCSI)
3
Clean needed
3
Clean Required
3
Drive Error
3
Media Error
3
TapeAlert flag set
The tape drive de-asserts the ACI_ATN_L line when the underlying conditions
causing the assertion no longer exist or when the automation controller
acknowledges receipt of the conditions using an Acknowledge Attention
command.
The ACI_ATN_L signal is an active low signal so the automation controller can
use it as a level or edge-triggered interrupt signal. As an alternative, the
ACI_ATN_L signal may connect to a general input port in the automation
controller microprocessor and the automation controller firmware may poll
this port at any desired frequency.
The automation controller can configure the tape drive to assert the
ACI_ATN_L line for all or any combination of the conditions listed above. The
automation controller configures the tape drive by setting the appropriate bits
in byte 12 of the Set Drive Configuration command.
In addition to the asynchronous notification feature, the tape drive reports all
of the conditions listed above when responding to a Get Drive Status
command. As a result, an automation controller engineer may make design