User`s guide

1.3.3 Environmental Monitor Unit (EMU)
The EMU provides increased protection against catastrophic subsystem faults.
The SW300 enclosure has two EMUs to provide complete system redundancy. If
one EMU should fail, the other continues to monitor all system functions. The
EMU works with the controller to warn the user of various types of existing or
impending subsystem failures. The controller responds to such conditions by
displaying error messages to the operator via the maintenance terminal and host
interfaces. At the same time, it controls the warning light emitting diodes (LEDs)
on the HS controller operator control panel (OCP) and the storage devices. The
EMU reports faults by turning on status LEDs on the SW300 front panel.
The EMU has a selectable audible alarm switch on the front panel:
• In the up (enable) position, the alarm is activated and produces an audible
signal whenever a fault condition occurs.
• In the down (disable) position, the alarm is deactivated.
The EMU performs the following specific functions:
• Monitors and controls the cabinet blowers—The EMU monitors the FAN_OK
signals coming from each of the eight blowers. If any blower malfunctions
(that is, its speed goes below a setpoint), the EMU turns all of the other
blowers up to high speed. This condition also generates a fault signal:
Turns on the Fault (amber) LED located on the upper right corner on the
front of the SW300
Turns on an LED on the EMU that identifies the defective blower
Turns off the SHELF_OK signal
Activates the audible alarm
The EMU monitors the FAN_INPLACE signals originating from each bank of
four blowers and detects if a blower is not installed or connected. If a blower
is not installed or connected, the EMU turns all of the other blowers up to
high speed. This condition also generates a fault signal:
– Turns on the Fault (amber) LED located on the upper right corner on the
front of the SW300
– Turns on a bank of LEDs on the EMU (thereby identifying the bank with
the missing blower)
– Turns off the SHELF_OK signal
– Activates the audible alarm
• Monitors the power supplies—The EMU monitors the POWER_OK signals
originating from all power supply SBBs. The EMU performs the following
actions if less than four power supply SBBs are functioning properly:
– Turns off the SYSTEM_POWER_OK signal going from the EMU
– Turns off the System OK (green) LED on the EMU
– Turns on the Shelf Fault (amber) LED on the EMU
– Turns off the System OK (green) LED located on the upper right corner
on the front of the SW300
– Turns on the Fault (amber) LED located on the upper right corner on the
front of the SW300
1–6 Introduction to the SW300 Enclosure