Scsi Cabling - ATTO Technology 1500D Installation And Operation Manual

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.
Exhibit 0.0-1 Various types of SCSI operate at different speeds and require different bus lengths to support
a certain number of devices.
STA terms
Fast SCSI
Fast/WIDE SCSI
UltraSCSI
Ultra/WIDE SCSI
WIDE Ultra SCSI
WIDE Ultra SCSI
Ultra2 SCSI
WIDE Ultra2 SCSI
Ultra 160 SCSI
Ultra 320 SCSI
Connecting SCSI devices to SCSI ports
ATTO iPBridge 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
iii
ATTO Technology Inc. iPBridge Installation and Operation Manual
Appendix B Cabling
Bus speed Bus
MB/sec. width
max. bits
10 8
20 16
20 8
40 16
40 16
40 16
40 8
80 16
160 16
320 16
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.
Max. bus lengths in meters
Single-
Differential
ended
3 25
3 25
1.5 25
n/a 25
1.5 n/a
3 n/a
n/a n/a
n/a n/a
n/a n/a
n/a 12
MB/sec. (Ultra, Ultra2, or Ultra160) transfer
rates.
You may use externally provided striping
software to create a RAID 0 group that includes
devices from both SCSI busses to increase overall
performance.
Max. device
support
LVD
n/a 8
n/a 16
n/a 8
n/a 16
n/a 8
n/a 4
12 8
12 16
12 16
n/a 16