HP Array Controller HSG V8.7 Software - Manual (Page 30)

Introducing the UltraSCSI RAID Enclosure
1–8 UltraSCSI RAID Enclosure
PVA
Each PVA functions only with its host enclosure and EMU. There is
no master PVA in the UltraSCSI RAID subsystem.
The PVA has the following primary functions:
• Allows the user to select the enclosure UltraSCSI bus ID.
• Enables the user to place the subsystem in a standby power mode
condition or return it to an operational status.
• In conjunction with the associated EMU, ensures that the major
components are functioning properly and notify the user and the
array controller of error or fault conditions.
Master Enclosure
Each UltraSCSI RAID subsystem (whether it has one, two, or three
enclosures) is under the control of the master enclosure. The
enclosure with the array controllers is the master enclosure. The EMU
in the master enclosure is the only EMU that can communicate
directly with the array controllers. In a multiple enclosure, or
expansion configuration, the master enclosure also communicates
with the other enclosures using the EMU-EMU communications bus.
The master enclosure PVA SCSI bus address setting is always 0.
Using address 0 automatically assigns SCSI bus device addresses 0,
1, 2, and 3 to the four drive SBB shelves.
Master EMU
The EMU in the master enclosure is the master EMU. Only the
master EMU communicates directly with the array controller. The
master EMU communicates with the expansion enclosure EMUs over
the EMU–EMU communications bus. The master EMU controls the
operation of the entire subsystem to include error detection, reporting,
and status displays.
Expansion Enclosure
An UltraSCSI RAID enclosure connected to the master enclosure
with cables is an expansion enclosure. Depending upon the array
controller, a subsystem can have a maximum of two expansion
enclosures. The expansion PVA SCSI bus address setting is either: