should schedule the upgrade during a non-peak I/O (low-usage) period. Use the
DS4800 Storage Manager performance monitor function to determine the
non-peak I/O load time if required.
v Cold-case upgrade procedure — The DS4800 storage subsystem is powered
down when controllers are upgraded.
Note:
The cold-case controller upgrade procedure is recommended if your
production environment allows the scheduling of downtime for
maintenance purposes.
Refer
to the IBM System Storage DS4800 Controller Upgrade Kit Instructions for
step-by-step instructions for upgrading DS4800 controller cache.
Replacing a power supply and fan unit
The power supply and fan unit is a component that includes both a 400-W power
supply unit and two fans. The power supply and fan units provide power and
cooling for the DS4800 Storage Subsystem. The power supply and fan units are
customer replaceable units (CRUs) and do not require preventive maintenance. Use
only the supported power supply and fan units for your specific storage subsystem.
Each power supply and fan unit has a built-in sensor that detects the following
conditions:
v Over-voltage
v Over-current
v Overheated power supply
If
any of these conditions occurs, one or both power supplies will shut down. If the
power remains off after the condition that causes it to go off, make sure that the
environment is optimal (no overheating has occurred, all electrical outlets are
working, and so on). For more information, see “Restoring power after an
unexpected shutdown” on page 110.
The storage subsystem cooling system consists of two fans in each of the two
power supply and fan units. The power supply and fan units circulate air from the
front to the back of the unit.
If both power supply and fan units fail, or if the power supply and fan units cannot
maintain an internal temperature below 70° C (158° F), the power supply and fan
units in the unit will automatically shut down (an over-temperature condition). If this
occurs, you must cool the unit and restart it. See “Restoring power after an
unexpected shutdown” on page 110.
Attention: The fans in the power supply and fan units draw in fresh air and force
out hot air. The power supply and fan units are hot-swappable and redundant;
however, if the fans in one power supply and fan unit fail, you must replace the
entire failed power supply and fan unit within 48 hours to maintain redundancy and
optimum cooling. Do not remove the failed power supply and fan unit from the
DS4800 chassis until you have the replacement power supply and fan unit. When
you do remove the failed power supply and fan unit, be sure to install the second
power supply and fan unit within 10 minutes to prevent any overheating due to the
interruption to the air flow that cools the DS4800 chassis.
Do not run the storage subsystem without adequate ventilation and cooling,
because it might cause damage to the internal components and circuitry.
152 IBM System Storage DS4800 Storage Subsystem: Installation, User’s, and Maintenance Guide
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