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The DWZZH-series UltraSCSI hubs are designed to allow more separation
between member systems and shared storage. Using the UltraSCSI hub also
improves the reliability of the detection of cable faults.
A side benefit is the ability to connect the member systems’ SCSI adapter
directly to a hub port without external termination. This simplifies the
configuration by reducing the number of cable connections.
A DWZZH UltraSCSI hub can be installed in:
• A StorageWorks UltraSCSI BA356 shelf (which has the required
180-watt power supply).
• A non-UltraSCSI BA356 that has been upgraded to the 180-watt power
supply with the DS-BA35X-HH option.
An UltraSCSI hub only receives power and mechanical support from the
storage shelf. There is no SCSI bus continuity between the DWZZH and
storage shelf.
The DWZZH contains a differential to single-ended signal converter for each
hub port (sometimes referred to as a DWZZA on a chip, or DOC chip). The
single-ended sides are connected together to form an internal single-ended
SCSI bus segment. Each differential SCSI bus port is terminated internal to
the DWZZH with terminators that cannot be disabled or removed.
Power for the DWZZH termination (termpwr) is supplied by the host bus
adapter or RAID array controller connected to the DWZZH port. If the
member system or RAID array controller is powered down, or the cable is
removed from the host bus adapter, RAID array controller, or hub port, the
loss of termpwr disables the hub port without affecting the remaining hub
ports or SCSI bus segments. This is similar to removing a Y cable when
using external termination.
The other end of the SCSI bus segment is terminated by the KZPSA-BB
or KZPBA-CB onboard termination resistor SIPs, or a trilink
connector/terminator combination installed on the HSZ40 or HSZ50.
The KZPSA-BB PCI-to-SCSI bus adapter:
• Is installed in a PCI slot of the supported member system (see
Section 2.3.2).
• Is a fast, wide differential adapter with only a single port, so only one
differential shared SCSI bus can be connected to a KZPSA-BB adapter.
• Operates at fast or slow speed and is compatible with narrow or wide
SCSI. The fast speed is 10 MB/sec for a narrow SCSI bus and 20 MB/sec
for a wide SCSI bus. The KZPSA-BB must be set to fast speed for
TruCluster Server.
Configuring Systems for External Termination or Radial Connections
to Non-UltraSCSI Devices 10–3