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storage arrays (HSZ70 and HSZ80), or RA8000 or ESA12000 storage
arrays (HSZ80 and HSG80). Older, non-UltraSCSI BA356 shelves are
supported with UltraSCSI host adapters and host RAID controllers as
long as they contain no UltraSCSI disks.
• UltraSCSI drives and fast wide drives can be mixed together in an
UltraSCSI BA356 shelf (see Chapter 9).
• Differential UltraSCSI adapters may be connected to either (or both)
a non-UltraSCSI BA356 shelf (via a DWZZB-VW) and the UltraSCSI
BA356 shelf (via the DS-BA35X-DA personality module) on the same
shared SCSI bus. The UltraSCSI adapter negotiates maximum transfer
speeds with each SCSI device (see Chapter 9).
• The HSZ70 and HSZ80 UltraSCSI RAID controllers have a wide
differential UltraSCSI host bus with a Very High Density Cable
Interconnect (VHDCI) connector. HSZ70 and HSZ80 controllers will
work with fast and wide differential SCSI adapters (for example,
KZPSA-BB) at fast SCSI speeds.
• Fast, wide SCSI drives (green StorageWorks building blocks (SBBs) with
part numbers ending in -VW) may be used in an UltraSCSI BA356 shelf.
• Do not use fast, narrow SCSI drives (green SBBs with part numbers
ending in -VA) in any shelf that could assign the drive a SCSI ID greater
than 7. It will not work.
• The UltraSCSI BA356 requires a 180-watt power supply (BA35X-HH).
It will not function properly with the older, lower-wattage BA35X-HF
universal 150-watt power supply (see Chapter 9).
• An older BA356 that has been retrofitted with a BA35X-HH 180-watt
power supply and DS-BA35X-DA personality module is still only FCC
certified for Fast 10 configurations (see Chapter 9).
3.2 SCSI Bus Performance
Before you set up a SCSI bus, it is important that you understand a number
of issues that affect the viability of a bus and how the devices connected to it
operate. Specifically, bus performance is influenced by the following factors:
• Transmission method (Section 3.2.2)
• Data path (Section 3.2.3)
• Bus speed (Section 3.2.4)
3.2.1 SCSI Bus Versus SCSI Bus Segments
An UltraSCSI bus may comprise multiple UltraSCSI bus segments. Each
UltraSCSI bus segment comprises electrical conductors that may be in a
Shared SCSI Bus Requirements and Configurations Using UltraSCSI Hardware 3–3