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4 How to connect SCSI devices to SCSI ports
TM
ATTO FibreBridge
SCSI ports are used to connect SCSI storage devices into the Fibre Channel
Storage Area Network (SAN).
A FibreBridge may have the following types of
SCSI ports:
➔ Ultra 2 (LVD) SCSI– 80 MB/sec. max per
bus
➔ Single Ended Ultra SCSI – 40 MB/sec.
max per bus
A FibreBridge with an LVD SCSI personality
module is downward compatible with Single
Ended Ultra SCSI as well as Fast, Wide, or
Narrow SCSI devices.
Each SCSI port is totally independent from the
any other SCSI port. This means that each bus is
capable of supporting 15 devices and each bus is
capable of 40 or 80 MB/sec. (Ultra or Ultra2).
However, you may use externally provided
software striping to create a RAID 0 group that
includes devices from both SCSI busses to
increase overall performance.
Another advantage of independent SCSI ports is
that each SCSI bus auto-negotiates the
appropriate sync rates with the connected devices.
If slower devices are mixed with faster Ultra2
devices, the bus will communicate at the rate of
the slowest device, thus wasting the performance
capabilities of the faster devices. You should
connect slower devices to one SCSI port and
connect faster devices on the other port on your
FibreBridge.
The FibreBridge supports a wide variety of SCSI
storage devices including stand-alone drives,
removable drives, JBODs, RAIDs, tape, CD and
DVD drives, changers, libraries and magneto
optical drives.
7 ATTO Technology FibreBridge 1190E Installation and Operation Manual
To connect SCSI devices to the ATTO
FibreBridge:
1
Connect a VHDCI SCSI connector from the
SCSI device to a port on the FibreBridge
1190.
Check the type of cable, cable length limit and
number of devices recommended for each port. It is
important to keep cable lengths as short as possible
to ensure the highest signal quality and
performance.These cable lengths include the wiring
inside the devices.
Device type
Ultra SCSI Single Ended
(SE)
Ultra SCSI Single Ended
(SE)
UltraSCSI High Voltage
Differential (HVD)
Ultra2 SCSI Low Voltage
Differential (LVD)
2
Set the IDs of the SCSI devices connected to
the bridge to a value other than 7. It is
recommended to use a sequential ID
starting at 0 for each device. Each SCSI port
in the ATTO FibreBridge has an internal
factory setting ID of 7, typical for a SCSI
initiator device.
NOTE The entire SCSI bus will operate at the speed of
the slowest device. If you wish to mix devices of different
SCSI speeds on the bridge, it is best to place them on
separate busses. That is, put the slower devices on
bridge SCSI bus 0, and the faster devices on bridge SCSI
bus 1. Each bus is independent so each can operate at
different speeds.
3
Terminate each SCSI bus after the last
device. The bridge is terminated internally.
Number of
Cable limit
devices
less than 4
3 meters
4 or more
1.5 meters
15
25 meters
15
12 meters
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