Technical data

This transmission method is less susceptible to noise than single-ended
SCSI and enables you to use longer cables. Devices with differential
SCSI interfaces include the following:
– KZPBA-CB
– KZPSA-BB
– HSZ40, HSZ50, HSZ70, and HSZ80 controllers
– Differential side of a SCSI signal converter or personality module
You cannot use the two transmission methods in the same SCSI bus
segment. For example, a device with a differential SCSI interface must be
connected to another device with a differential SCSI interface. If you want to
connect devices that use different transmission methods, use a SCSI signal
converter between the devices. The DS-BA35X-DA personality module is
discussed in Section 10.1.2.2. See Section 10.1 for information about using
the DWZZ* series of SCSI signal converters.
You cannot use a DWZZA or DWZZB signal converter at UltraSCSI speeds
for TruCluster Server if there are any UltraSCSI disks on the bus, because
the DWZZA or DWZZB will not operate correctly at UltraSCSI speed.
The DS-BA35X-DA personality module contains a signal converter for
the UltraSCSI BA356. It is the interface between the shared differential
UltraSCSI bus and the UltraSCSI BA356 internal single-ended SCSI bus.
RAID array controller subsystems provide the function of a signal converter,
accepting the differential input and driving the single-ended device buses.
3.2.3 Data Path
There are two data paths for SCSI devices:
• Narrow — Implies an 8-bit data path for SCSI-2. The performance of
this mode is limited.
• Wide — Implies a 16-bit data path for SCSI-2 or UltraSCSI. This mode
increases the amount of data that is transferred in parallel on the bus.
3.2.4 Bus Speed
Bus speeds vary depending upon the bus clocking rate and bus width, as
listed in Table 3–1.
Shared SCSI Bus Requirements and Configurations Using UltraSCSI Hardware 3–5