Scsi Cabling; Cable Types - ATTO Technology FastStream VT 5300 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.
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
Fast SCSI
Fast/WIDE SCSI
UltraSCSI
Ultra/WIDE SCSI
Ultra/WIDE SCSI
Ultra/WIDE SCSI
Ultra2 SCSI
Ultra2/WIDE SCSI
Ultra160/WIDE SCSI
Ultra320 SCSI
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
iii
ATTO Technology Inc. FastStream VT 5300 Installation and Operation Manual
Appendix B
Bus speed Bus
MB/sec. width
maximum bits
10 8
20 16
20 8
40 16
40 16
40 16
80 16
80 16
160 16
320 16
Cabling

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.
Max. bus lengths in meters
Single-
Differential
ended
3 25
3 25
1.5 25
NA 25
1.5 NA
3 NA
NA NA
NA NA
NA NA
NA NA
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.
Maximum
device
LVD
support
NA 8
NA 16
NA 8
NA 16
NA 8
NA 4
12 8
12 16
12 16
12 16