SCSI to SCSI RAID Subsystem
User Manual
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4.2 SCSI Concepts
Before configuring the subsystem, you must first understand some basic SCSI concepts
so that the subsystem and SCSI devices will function properly.
4.2.1 Multiple SCSI Format Support
The subsystem support the SCSI interface standards listed below. Note that the data bit
and cable length restrictions must be followed.
SCSI Type
Data Bit
Data Rate
Cable
Length
SCSI-1
8 Bits
5 MB/Sec
6 m
Fast SCSI
8 Bits
10 MB/Sec
3 m
Fast Wide SCSI
16 Bits
20 MB/Sec
3 m
Ultra SCSI
8 Bits
20 MB/Sec
1.5 m
Ultra Wide SCSI
16 Bits
40 MB/Sec
1.5 m
Ultra 2 SCSI
8 Bits
40 MB/Sec
12 m
Ultra 2 Wide SCSI
16 Bits
80 MB/Sec
12 m
Ultra 160 Wide LVD
16 Bits
160MB/Sec
12 m
Ultra 320 LVD
16 Bits
320MB/Sec
12 m
4.2.2 Host SCSI ID Selection
A SCSI ID is an identifier assigned to SCSI devices which enables them to communicate
with a computer when they are attached to a host adapter via the SCSI bus. Each SCSI
device, and the host adapter itself, must have a SCSI ID number (Ultra 320 LVD SCSI =
0 to 15). The ID defines each SCSI device on the SCSI bus. If there are more than one
SCSI adapters in the Host system, each adapter forms a separate SCSI bus. SCSI IDs
can be reused as long as the ID is assigned to a device on a separate SCSI bus. Refer to
the documentation that came with your peripheral device to determine the ID and how
to change it. The subsystem must be assigned a unique SCSI ID ranging from 0 to 15 for
the Ultra 320 LVD SCSI host system. The default value is ID 0.
4.2.3 Terminators
Based on SCSI specifications, the SCSI bus must be terminated at both ends, meaning
the devices that are connected to the ends of the SCSI bus must have their bus
terminators enabled. Devices connected in the middle of the SCSI bus must have their
terminators disabled. Proper termination allows data and SCSI commands to be
transmitted reliably on the SCSI bus. The host adapter and the SCSI devices attached to
it must be properly terminated, or they will not work reliably. Termination means that
terminators are installed in the devices at each end of the bus.
NOTE: If your RAID subsystem is the last device on the SCSI bus,
attach the terminator included in the package to the Host Channel
A Out port and/or B Out port before using the subsystem
.
