The storage unit has four power on modes: standby power, dual power supply active, single power supply active, and battery backup mode.
Standby power mode
The storage unit is in standby power mode when the unit is completely installed and receiving ac power, but the power supplies are not generating dc power. Standby dc power is delivered to the power distribution system to maintain basic power management and control. This mode can occur with either one or two power supplies.
Dual power supply active mode
The storage unit is in dual power supply active mode when both power supplies are actively receiving ac power and generating both main and standby dc power. Both power supplies are sharing the power supply requirements for the entire storage unit. Dual power supply active mode is the normal operating mode for the server enclosure.
Single power supply active mode
The storage unit is in single power supply active mode when only one power supply is actively receiving ac power and generating both main and standby dc power. This single power supply is generating all of the power required to operate the storage unit.
Battery backup mode
The storage unit is in battery backup mode when ac power loss has occurred and the battery backup units are supplying dc power to only those resources that are required to maintain data integrity. When power loss occurs on a storage unit, the processor card initiates a flush of all processor hardware caches into server memory. The power-on sequence automatically begins once ac power is delivered to the power supplies.