Connecting The Tape Library; Dual Scsi Busses - Sun Microsystems SPARCstorage Library Installation And User Manual

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Connecting the Tape Library

The following procedures explain how to install a tape library in a direct
connection to a desktop system, and how to install a tape library in a daisy
chain connection with other external peripherals and a desktop system.
Note – The tape library only uses single-ended SCSI cables and not the
differential SCSI cables commonly used with disk drives.
There are four SCSI ports on the back panel of the tape library. Use these
connectors to enable multiple devices to be connected in a series for daisy
chained configurations.
If the tape library is not the last physical device on the SCSI bus, plug a SCSI
cable into each connector. If the tape library is the last physical device on the
SCSI bus, plug a SCSI cable into one of the connectors and the appropriate
SCSI external terminator into the other connector.
If you are connecting the tape library to a single SCSI bus, you must install the
SCSI bus jumper block into the middle two connectors. If you are installing the
tape library on two SCSI buses, the SCSI bus jumper block is not needed.

Dual SCSI Busses

In the tape library, you can separate the internal SCSI bus into two busses. One
drive and the robotic arm are on one bus, the second drive is on the other bus.
You can put the entire unit on one bus by installing the provided jumper block
across the middle SCSI connectors on the tape library rear panel.
For most installations, the single bus is preferred. Other than some fault
tolerance there is no significant advantage to the dual bus configuration. There
is no throughput advantage to having the internal drives on two busses except
in the extreme case of very non-compressible data when using data
compression on the drives. And, with the dual bus configuration, control and
access by the applications software can be an issue. You must verify that the
your software can support separating the second drive onto a separate SCSI
bus or separate host system.
Installing the SPARCstorage Library 2-17