ATTO Technology SC 5700 operation manual Appendix C Scsi Cabling, Cable types

Appendix C SCSI Cabling

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

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.

1Connect the cable from the SCSI device to a SCSI port on the FastStream.

2Check 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.

3Set 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.

4Terminate the SCSI bus after the last device. The FastStream is terminated internally.

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ATTO Technology Inc. FastStream SC Installation and Operation Manual