Dell EMC PowerEdge R740 - Hot Spare Feature

NOTE: When two identical PSUs are installed, power supply redundancy (1+1 – with redundancy or 2+0 – without redundancy) is
congured 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 eciency.
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 signicantly 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 eciency. 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 ecient 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 congure the hot spare feature by using the iDRAC settings. For more information, see the iDRAC User’s Guide available at
Dell.com/poweredgemanuals.
Removing a power supply unit blank
Prerequisite
Follow the safety guidelines listed in Safety instructions.
Step
If you are installing a second power supply unit (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
conguration. Remove the PSU blank only if you are installing a second PSU.
Figure 127. Removing a power supply unit blank
Next step
Install the PSU blank.
170
Installing and removing system components