Storage Architecture; The Expansion Unit - Compaq SW TL881 DLT Mini-Lib/1 Manual

The TL881MiniLibrary Base Module
The MiniLibrary Expansion Unit (Master)
The MiniLibrary Data Unit
The Pass-Thru Mechanism
Every Pass-Thru Mechanism has one Expansion Unit and any combination of
up to eight of the remaining components stacked in a rack. The Expansion
Unit can move media freely within itself and between the MiniLibrary Base
Modules and the Data Units with the Pass-Thru Mechanism™.
In the MiniLibrary system, you can combine modules to provide the right
combination of capacity and performance for your requirements. The
architecture allows you to change or add to the mix of modules to optimize
throughput, capacity, or both as your storage requirements change.
When connected as a system, the robotics in MiniLibrary Base Modules and
Data Units operate from Expansion Unit commands. The host computer(s) are
not dependent on the internal geometry of the system, or on the actions or
capabilities of any of the slave modules. The Expansion Unit presents, to the
host(s), a single SCSI medium changer device with a single SCSI Medium
Transport element, several SCSI storage elements equal to the number of
cartridge magazine slots, several SCSI Import/Export elements as specified by
the user during configuration of the Expansion Unit, and a number of SCSI
Data Transfer elements equal to the total number of drives in the system.

Storage Architecture

The MiniLibrary architecture is uniquely suited and designed for expanding
storage needs. The MiniLibrary architecture enables the robotics in each of the
MiniLibrary components to exchange cartridges with the Pass-Thru
Mechanism, and integrates the robotics in the individual components and the
Pass-Thru Mechanism into a single, high-performance library robotics system.
The MiniLibrary is easily modified – by adding modules and extending the
Pass-Thru Mechanism – to adapt to expanding storage needs. You can add
drives for faster performance or magazine space for greater capacity, as
needed. At power-up the MiniLibrary updates the system map, signaling the
host of the need for expansion.

The Expansion Unit

The Master Expansion Unit integrates the robotics in the individual modules
into a single coordinated library robotics system. The Expansion Unit
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