Appendix C Scsi Cabling; Cable Types; Connecting Scsi Devices To Scsi Ports - ATTO Technology FastStream SC 5700 Installation And Operation Manual

Additional information to physically connect ports to devices and to your SAN.
SCSI cables and devices must be chosen to maximize
performance and minimize the electrical noise from
the high-speed data transfers available with the SCSI
protocol. Cabling and termination methods become
important considerations for proper performance.
SCSI cables and devices are subject to specific length
and number limitations to deal with electrical problems
that arise at increased operating speeds.

Cable types

Use high-quality cables rated for the type of SCSI
transfers required: well-insulated SCSI cables ensure
error free communications.
Try to keep cable lengths as short as possible to
ensure higher signal quality and performance. See
Exhibit A-2 on page xxiv.
Note
UltraSCSI is very sensitive to SCSI bus noise,
cable distances and the number of devices
connected on the SCSI bus. Carefully connect
your devices when working with UltraSCSI.

Connecting SCSI devices to SCSI ports

SCSI ports connect SCSI storage devices to the
network. Each SCSI port is totally independent from
the other SCSI port.
Each SCSI port is a bus capable of supporting 16
devices and each bus is capable of 40, 80 or 160
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ATTO Technology Inc. FastStream SC Installation and Operation Manual
Appendix C SCSI Cabling
MB/sec. (Ultra, Ultra2, Ultra160 or Ultra 320) transfer
rates.
Each SCSI bus auto-negotiates the appropriate sync
rates with the connected devices. If slower devices are
mixed with faster devices, the bus communicates at
the rate of the slowest device, thus wasting the
performance capabilities of the faster devices.
Connect slower devices to one SCSI port and connect
faster devices to the other port.
The FastStream supports a wide variety of SCSI
storage devices including stand-alone and removable
drives.
1 Connect the cable from the SCSI device to a
SCSI port on the FastStream.
2 Check the type of cable, cable length limit and
number of devices recommended for the port.
See Exhibit A-2 on page xxiv.
Keep cable lengths as short as possible to
ensure the highest signal quality and
performance. These cable lengths include the
wiring inside the devices.
3 Set the IDs of the SCSI devices connected to
the FastStream to a value other than 7.
Use a sequential ID starting at 0 for each device.
The SCSI port has an internal factory setting ID
of 7, typical for a SCSI initiator device.
4 Terminate the SCSI bus after the last device.
The FastStream is terminated internally.