NStor Technologies Disk Array Enclosure User Manual download pdf (Page 32)

Installation

Cabling Configuration

Cabling Conﬁguration

The Ultra Wide SCSI mode provides enhanced performances with data transfers

up to 40 MBs per second (20 MHz), while the Fast Wide SCSI mode will provide

transfers up to 20 MBs per second (10 MHz).

The cabling conﬁguration section is divided into two subsections, Ultra Wide

SCSI and Fast Wide SCSI. These two sections provide the recommended cable

conﬁgurations when operating the CR8e in a speciﬁc mode.

The CR8e supports the American National Standard Ultra SCSI (Fast-20) parallel

interface standards, referred to as Ultra Wide SCSI. This standard is backward

compatible with Fast SCSI (SCSI-2 with the Wide option), also referred to as Fast

Wide SCSI. This standard deﬁnes the mechanical, electrical, and timing

requirements. In compliance with these interface standards, certain limitations

apply when considering the conﬁguration, lengths of cabling, and termination.

The conﬁguration samples and cables provided with the subsystem meet the

requirements of the speciﬁcations. Modiﬁcations to any of these variables can

have less than desirable results when operating any SCSI device.

General

Cables

Cable length is a critical consideration when conﬁguring the subsystems. There

are different limitations for Ultra Wide SCSI and Fast Wide SCSI.

When calculating the total length of your cabling, the internal subsystem length

of cables and printed circuit board traces (known as the internal cable length)

must be subtracted from your total cable length. The CR8e internal cable length is

36 inches.

For Ultra Wide SCSI, the total SCSI cable length is 3 meters (118 inches) with

four drives and 1.5 meters (59 inches) with eight drives. After subtracting the

internal length of 36 inches the remaining cable length is 82 inches or

approximately 6.83 feet (2.08 meters) for four drives and 23 inches or

approximately 1.9 feet (.58 meters) for eight drives.

For Fast Wide SCSI, the total SCSI cable length is 6 meters (236 inches) with

four drives and 3 meters (118 inches) with eight drives. After subtracting the

internal length of 36 inches the remaining cable length is 200 inches or

approximately 16.66 feet (5.08 meters) for four drives or approximately 6.83

feet (2.08 meters) for eight drives.

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NStor Technologies Disk Array Enclosure User Manual Page 32