ATTO Technology 2500C operation manual Appendix B Cabling, Scsi cabling, Cable types, Examples

Appendix B 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.

Examples

The SCSI specification limits total bus cable length for single-ended SCSI in a non-UltraSCSI environment to 3 meters (combined length of both internal and external cable lengths).

In an UltraSCSI workgroup environment with a 7- drive tower, you are limited to 1.5 meters between the host and the tower, including the cabling for the tower. If the 7-drive tower requires 1 meter of cabling to connect all of its drives, the distance from the tower to the host must be .5 meters.

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 0.0-1 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			Max. device
	MB/sec.	width
STA terms			Single-	Differential	LVD	support
	max.	bits
			ended
Fast SCSI	10	8	3	25	n/a	8
Fast/WIDE SCSI	20	16	3	25	n/a	16
UltraSCSI	20	8	1.5	25	n/a	8
Ultra/WIDE SCSI	40	16	n/a	25	n/a	16
Ultra/WIDE SCSI	40	16	1.5	n/a	n/a	8
Ultra/WIDE SCSI	40	16	3	n/a	n/a	4
Ultra2 SCSI	80	16	n/a	n/a	12	8
Ultra2/WIDE SCSI	80	16	n/a	n/a	12	16
Ultra3/WIDE SCSI	160	16	n/a	n/a	12	16

Connecting SCSI devices to SCSI ports ATTO iPBridge SCSI ports connect SCSI storage devices to the network. Each SCSI port is completely independent from the other SCSI port.

iii

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 Ultra3) transfer rates.

You may use externally provided striping software to create a RAID 0 group that includes

ATTO Technology Inc. iPBridge Installation and Operation Manual