Digital Equipment StorageWorks UltraSCSI DS-BA370 Series, User Manual

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Introducing the Ultra SCSI RAID Enclosure
1–8 UltraSCSI RAID Enclosure
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In conjunction with the associated EMU, ensures that the major
components are functioning properly and notifies the user and the array
controller of error or fault conditions. Each PVA functions only with its
host enclosure and EMU. There is no master PVA in the UltraSCSI
RAID subsystem.
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 these
enclosures is the only EMU that can communicate directly with the array
controllers. In a multiple enclosure, or expansion configuration, this
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 disk drive shelves.
Master EMU
The environmental monitoring unit in the master enclosure is the Master
EMU. This is the only EMU that communicates directly with the array
controller and the expansion enclosure EMUs over the EMU—EMU
communications bus. This 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:
2–to establish SCSI bus device addresses 8, 9, 10, and 11.
3– to establish SCSI bus device addresses 12, 13, 14, and 15.
____________________ Caution ____________________
Not all array controllers support an UltraSCSI RAID subsystem
with more than one enclosure. Read the array controller
documentation to ensure the controller supports expanded
configurations.
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