Appendix a cabling, Scsi cabling, Cable types – ATTO Technology 1550D User Manual
Page 30: Examples, Scsi cabling cable types examples, Cabling
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ATTO Technology Inc. iPBridge Installation and Operation Manual
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.
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 A-1 Various types of SCSI operate at different speeds and require different bus lengths to support
a certain number of devices.
STA terms
Bus speed
MB/sec.
max.
Bus
width
bits
Max. bus lengths in meters
Max. device
support
Single-
ended
Differential
LVD
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
WIDE Ultra SCSI
40
16
1.5
n/a
n/a
8
WIDE Ultra SCSI
40
16
3
n/a
n/a
4
Ultra2 SCSI
40
8
n/a
n/a
12
8
WIDE Ultra2 SCSI
80
16
n/a
n/a
12
16
Ultra 160 SCSI
160
16
n/a
n/a
12
16
Ultra 320 SCSI
320
16
n/a
12
n/a
16