Owners Manual

Power supply units
The power supply unit (PSU) is an internal hardware component which supplies power to the components in the system.
This system supports two 750 W AC PSUs.
CAUTION: If two PSUs are installed, both the PSUs must have the same type of label. For example, Extended
Power Performance (EPP) label. Mixing PSUs from previous generations of storage systems are not supported,
even if the PSUs have the same power rating. Mixing PSUs will result in mismatch condition or failure to turn
the system on.
NOTE: When two identical PSUs are installed, power supply redundancy (1+1 – with redundancy or 2+0 – without
redundancy) is configured in system BIOS. In redundant mode, power is supplied to the system equally from both PSUs
when Hot Spare is disabled. When Hot Spare is enabled, one of the PSUs is put into the sleep mode when system utilization
is low in order to maximize efficiency.
NOTE: If two PSUs are used, they must be of the same maximum output power.
Hot spare feature
Your system supports the hot spare feature that significantly reduces the power overhead associated with power supply unit
(PSU) redundancy.
When the hot spare feature is enabled, one of the redundant PSUs is switched to the sleep state. The active PSU supports 100
percent of the system load, thus operating at higher efficiency. The PSU in the sleep state monitors output voltage of the active
PSU. If the output voltage of the active PSU drops, the PSU in the sleep state returns to an active output state.
If having both PSUs active is more efficient than having one PSU in the sleep state, the active PSU can also activate the
sleeping PSU.
The default PSU settings are as follows:
● If the load on the active PSU is more than 50 percent of PSU rated power wattage, then the redundant PSU is switched to
the active state.
● If the load on the active PSU falls below 20 percent of PSU rated power wattage, then the redundant PSU is switched to
the sleep state.
You can configure the hot spare feature by using the iDRAC settings.
For more information, see the Integrated Dell Remote Access Control User's Guide located at www.dell.com/idracmanuals.
Removing a power supply unit blank
Prerequisites
Follow the safety guidelines listed in Safety instructions.
Steps
If you are installing a second PSU, remove the PSU blank in the bay by pulling the blank outward.
CAUTION:
To ensure proper system cooling, the PSU blank must be installed in the second PSU bay in a
non-redundant configuration. Remove the PSU blank only if you are installing a second PSU.
Installing and removing system components 103