User`s guide

1-2 TL891 MiniLibrary System User's Guide
Compaq Confidential – Need to Know Required
Writer: Everett Godaire Project: TL891 MiniLibrary System User's Guide Comments:
Part Number: ER-TL891-UA.A01 File Name: b-ch1 Introduction Last Saved On: 3/1/99 4:07 PM
MiniLibrary Storage Architecture
When connected as a system, the robotics in the MiniLibrary Expansion Unit
act as commanded by the host computer(s). The host(s) need no knowledge of
the internal geometry of the system, or of the actions or capabilities of the
Base Modules.
The Expansion Unit presents to the host(s) a single SCSI medium changer
device with a single SCSI Medium Transport element, a number of SCSI
Storage elements equal to the total number of cartridge magazine slots, a
number of 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.
Flexibility
Compaq’s MiniLibrary storage architecture is uniquely suited to growing
storage needs. Its flexible library robotics system enables you to start with a
system configured to your present requirements, confident that as your storage
needs evolve, you can easily modify the MiniLibrary by adding modules and
extending the pass-through mechanism. 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 Expansion Unit 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 Expansion Unit 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 buses 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.