Scsi Terminology; Setting Up The Scsi Bus - Tandberg Data DAT 160 User Manual

Chapter 8–SCSI configuration guide

SCSI terminology

Setting up the SCSI bus

DAT SCSI Tape Drives
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is not recommended, as performance will be severely impacted and
complicated bus configuration is required to overcome bus termination
issues.
Make sure that the last device on the SCSI bus is terminated. We recommend
that you do not attach the tape drive to the same SCSI bus as the disk drive.
See "SCSI termination" on page 52 for more information about terminating
DAT tape drives.
SCSI is a bus interface: all the devices are connected to a single cable
(some of this may be inside and some outside the host computer's case).
The connection to the host itself is known as the Host Bus Adapter (HBA).
You can have several HBAs in a single computer, each with its own SCSI
bus: this is a common arrangement in high-performance servers. Some host
bus adapters (such as the LSI Logic LSI22320-R) have more than one SCSI
bus available on a single card.
Various terms are used when describing SCSI devices. These terms relate
to the factors that affect performance and cable length:
• The speed of the data bus, which may be Fast, Ultra, Ultra2, Ultra3, Ul-
tra160 or Ultra320.
• The width of the data bus, which may be Narrow or Wide (8-Bit or 16-
Bit).
• The voltage level of the interface, which may be single-ended (SE) or
low voltage differential (LVD).
DAT drives are Ultra 160 SCSI devices designed to operate on a low voltage
differential SCSI interface.
Each device on a SCSI bus, including the SCSI host bus adapter (HBA),
must be configured with a unique ID (identifier). The SCSI bus must be
terminated.
Note: We recommend that a dedicated host bus adapter is used
for the tape drive. A suitable adapter is available from your
supplier as an accessory.
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