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ATTO Technology Inc. FastStream VT 5300 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.
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.
Connecting SCSI devices to SCSI ports
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
MB/sec. (Ultra, Ultra2 or Ultra160) transfer rates.
Each SCSI bus auto-negotiates the appropriate
sync rates with the connected devices. If slower
devices are mixed with faster devices, the bus
communicates at the rate of the slowest device,
thus wasting the performance capabilities of the
faster devices. Connect slower devices to one
SCSI port and connect faster devices to the other
port.
The FastStream supports a wide variety of SCSI
storage devices including stand-alone drives,
removable drives, JBODs, RAIDs, tape, CD and
DVD drives, changers and libraries.
STA terms
Bus speed
MB/sec.
maximum
Bus
width
bits
Max. bus lengths in meters
Maximum
device
support
Single-
ended
Differential LVD
Fast SCSI
10 8 3 25 NA 8
Fast/WIDE SCSI
20 16 3 25 NA 16
UltraSCSI
20 8 1.5 25 NA 8
Ultra/WIDE SCSI
40 16 NA 25 NA 16
Ultra/WIDE SCSI
40 16 1.5 NA NA 8
Ultra/WIDE SCSI
40 16 3 NA NA 4
Ultra2 SCSI
80 16 NA NA 12 8
Ultra2/WIDE SCSI
80 16 NA NA 12 16
Ultra160/WIDE SCSI
160 16 NA NA 12 16
Ultra320 SCSI
320 16 NA NA 12 16