LaCie d2 SCSI Hard Drive

Appendix - SCSI Q & A

 

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8. Appendix 1 – SCSI Questions and Answers

For the new user, SCSI terminology can be a little daunting. The table below was designed to help you get a clearer understanding of what the different SCSI names mean and their performance characteristics.

Before you read the chart, let’s define what we mean by Standard, Protocol and Industry names:

Standard - The broadest category, featuring general guidelines given by the various industry groups and standards associa- tions. There are three SCSI standards: SCSI-1, SCSI-2 and SCSI-3.

Protocols – Sub-categories of SCSI standards with defining specific characteristics and features. "Narrow" and "Wide", for example, tell us about the bus width of a particular type of device.

Industry names – Names used by computer hardware manufacturers to describe SCSI devices to potential buyers.

Standard

Protocols

Industry Names

Bus Width

Signaling

Throughput

SCSI-1

"Regular" SCSI

SCSI-1, SCSI

Narrow (8-bit)

SE/HVD

Up to 5MB/s

 

 

 

 

 

 

SCSI-2

Wide SCSI

Wide SCSI-2

Wide (16-bit)

SE/HVD

to 10MB/s

 

Fast SCSI

Fast SCSI-2

Narrow (8-bit)

SE/HVD

to 10MB/s

 

Fast Wide SCSI

Fast Wide SCSI-2

Wide (16-bit)

SE/HVD

to 10MB/s

 

 

 

 

 

 

to 20MB/s

 

 

 

 

 

 

 

SCSI-3

Ultra SCSI

Fast-20

SCSI

Narrow (8-bit)

SE/HVD

to 20MB/s

 

Wide Ultra SCSI

Fast-20

Wide SCSI/Ultra

Wide (16-bit)

SE/HVD

to 40MB/s

 

 

Wide SCSI

 

 

 

 

Ultra2 SCSI

Fast-40

SCSI/Narrow

Narrow (8-bit)

LVD

to 40MB/s

 

 

Ultra2 SCSI

 

 

 

 

Wide Ultra2 SCSI

Wide Fast-40 SCSI/Ultra2

Wide (16-bit)

LVD

to 80MB/s

 

 

SCSI/Ultra2 Wide SCSI

 

 

 

 

Ultra3 SCSI

Fast-80

SCSI

Wide (16-bit)

LVD

to 160MB/s

 

Ultra 160 SCSI

Ultra 160/m SCSI

Wide (16-bit)

LVD

to 160MB/s

 

Ultra 160+ SCSI

 

 

Wide (16-bit)

LVD

to 160MB/s

 

Ultra320 SCSI

Ultra4 SCSI/Fast-160 SCSI

Wide (16-bit)

LVD

to 320MB/s

 

 

 

 

 

 

 

What issues are involved when mixing Narrow SCSI and Wide SCSI devices on the same SCSI chain?

The simplest SCSI configurations use only Narrow devices, or only Wide devices. In this type of configuration, you choose the correct cable, connect all of the devices in a bus topology, and place the appropriate type of termination at both ends of the bus. In this case, termination is relatively straightforward because all of the devices have the same width.

Sometimes, however, you may need to mix Narrow and Wide devices on a single SCSI channel. This is becoming increasingly common as the newest hard drives are Wide only, but many other kinds of devices are still produced for the Narrow interface.

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LaCie KY0730482 warranty Appendix 1 Scsi Questions and Answers