Compaq AA-RHGWB-TE manual

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 2.4.1).

•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