IBM DS5100 Installation, User's, And Maintenance Manual page 216

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 136.
Attention:
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
DS5100 and DS5300 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 chassis.
Do not run the storage subsystem without adequate ventilation and cooling,
because it might cause damage to the internal components and circuitry.
Use the following procedure to replace a power supply and fan unit. Each power
supply and fan unit contains a power supply, cooling fan, battery charger, and
temperature sensor. If any of these components fail, you must replace power supply
and fan unit. The power supply, fan, battery charger, and temperature sensor are
not individually replaceable components within the power supply and fan unit.
Statement 8:
CAUTION:
Never remove the cover on a power supply and fan unit or any part that has
the following label attached.
Hazardous voltage, current, and energy levels are present inside any
component that has this label attached. There are no serviceable parts inside
these components. If you suspect a problem with one of these parts, contact
a service technician.
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IBM System Storage DS5100 and DS5300 Storage Subsystem: Installation, User's, and Maintenance Guide
The fans in the power supply and fan units draw in fresh air and force
1. Use the DS Storage Manager client software to print a storage subsystem
profile.
2. Locate the storage subsystem that contains the failed power supply and fan
unit by checking the Overall Configuration Needs Attention LED on the front
bezel of the storage subsystem. (Figure 115 on page 185 shows the location of
the Overall Configuration Needs Attention LED on the front bezel.)