ATTO Technology 5300, FastStream VT operation manual Appendix a Cabling, Scsi cabling, Cable types

Appendix A Cabling

Additional information to physically connect ports to devices and to your SAN.

SCSI cabling

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.

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.

Exhibit A-1 Various types of SCSI operate at different speeds and require different bus lengths to support a certain number of devices.

	Bus speed	Bus	Max. bus lengths in meters			Maximum
	MB/sec.	width				device
STA terms			Single-	Differential	LVD
	maximum	bits				support
			ended
Fast SCSI	10	8	3	25	NA	8
Fast/WIDE SCSI	20	16	3	25	NA	16
UltraSCSI	20	8	1.5	25	NA	8
Ultra/WIDE SCSI	40	16	NA	25	NA	16
Ultra/WIDE SCSI	40	16	1.5	NA	NA	8
Ultra/WIDE SCSI	40	16	3	NA	NA	4
Ultra2 SCSI	80	16	NA	NA	12	8
Ultra2/WIDE SCSI	80	16	NA	NA	12	16
Ultra160/WIDE SCSI	160	16	NA	NA	12	16
Ultra320 SCSI	320	16	NA	NA	12	16

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 15 devices and each bus is capable of 40, 80 or 160 MB/sec. (Ultra, Ultra2 or Ultra160) 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

i

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 drives, removable drives, JBODs, RAIDs, tape, CD and DVD drives, changers and libraries.

ATTO Technology Inc. FastStream VT 5300 Installation and Operation Manual