Smartscale Storage™ Architecture; The Global Control Module - Overland Data DLT LibraryXpress Series Service Manual

SmartScale Storage™ Architecture
Flexibility
The DLT LibraryXpress Smartscale Storage™ architecture is uniquely suited to growing
storage needs. Overland Data's Smartscale Storage architecture enables the robotics in each
of the LibraryXpress modules to exchange cartridges by means of the XpressChannel™ pass-
through elevator, and integrates the robotics in the individual modules and the Global
Control's XpressChannel into a single high-performance library robotics system. You can
start with a system configured to your present requirements, confident that as your storage
needs evolve, the LibraryXpress can easily be modified by adding modules and extending the
XpressChannel. Add drives for faster performance or magazine space for greater capacity, as
needed. Then just turn on the power, and immediately the system updates the system map so
the host is informed of the expanded capability.
Multi-Server Data Sharing
A host computer with a SCSI controller connected to a bus is a SCSI Initiator. The Global
Control Module is a SCSI Target. SCSI rules permit multiple Initiators on a single bus.
Therefore, with the proper host software, it is possible to connect multiple hosts to a single
Global control Module over a single SCSI bus. This allows multiple hosts to operate the
library robotics, loading and unloading cartridges as each host requires.
In a system with many drives, it is desirable to use multiple SCSI busses for the drives, so the
data transfer rate of the drives is not limited by bus bandwidth. In a large, high-performance
system, drives may be connected to separate hosts. Using special software, one of the hosts
can act as a master server, processing all robotics commands. In this way several hosts may
share a common data base.

The Global Control Module

Description
The LXG5016 Global Control Module integrates the robotics in the individual modules into a
single coordinated library robotics system. The Global Control Module performs and
maintains an inventory of all media present in the system, including bar code data, if the
modules are equipped with bar code readers. All necessary system control operations may be
performed from the control panel of the Global Control Module, as well as from the host via
software. The SCSI interface for the library robotics is designed for high-speed
communication with the host, and is available in standard SCSI-2, Fast SCSI-2 or Fast/Wide
SCSI configurations.
In addition to its system control functions, the Global Control Module has a 16-cartridge
magazine with a rugged random access robotic mechanism. The module robotics moves
cartridges between the XpressChannel and any of the 16 cartridge storage locations.
The user may designate a magazine in one of the slave modules as a mail slot for inserting or
removing one or more single cartridges, which implements the SCSI Import/Export
commands. Note: a magazine which has been reserved for Import/Export service may not be
used for data storage.
2 Chapter 1 - Introduction