Battery backup unit

The battery backup unit provides reserve power and data integrity function in the case of a loss of the main power supply.

The battery backup units are located horizontally in the middle of the rear of the enclosure.

Battery backup units (BBUs) provide protection against data loss in the event of a power failure. The storage unit includes a redundant battery backup unit for each ac/dc power supply. Each BBU is charged by the associated power supply. The battery backup unit can provide enough backup power to preserve data integrity for up to 72 hours without power. The battery does not back up the memory if all nonvolatile data has already been moved to disk storage.

Note: The BBU must charge before initialization can occur.

In the event that input power is lost to the cluster when there is modified customer data that has not been moved to disk storage, the cluster converts to battery backup mode. In battery backup mode, the BBU supplies an alternate source of dc power to only those cluster components that are required to preserve data integrity and provide indication of the cluster power state. If input power is restored, the cluster automatically initiates the power-on activation sequences to recover the system and conserve battery power.

During BBU service, if, after removing a battery backup unit, you choose not to immediately replace the resource, you must fill the empty BBU slot with a battery backup unit blank to prevent your storage unit from overheating. Figure 1 shows a drawing of a battery backup unit blank. If you do not replace the battery backup unit, or if you insert a blank unit, the processor card associated with the missing battery remains offline and your server or storage unit operates in a mode that risks data loss in the event of a failure.

Figure 1. Battery backup unit blank

The battery backup unit contains a dc present indicator, a charging state indicator, and a service/fault indicator. The descriptions of the states for the BBU indicators are described in Table 1. Figure 2 shows the location of these indicators.

Figure 2. Battery backup unit indicators

LED indicators on the battery backup unit

Table 1. LED indicator states for the battery backup unit
Indicator name (color)	Purpose	State descriptions
dc present (green)	Indicates that power is being delivered to the battery backup units.	Solid: +5 Volt dc and +12 Volt dv power is present. Off: No power is being delivered to the BBU.
Charging state (green)	Indicates the level of charge for the battery.	Solid: The BBU is fully charged. Flashing (slow): The BBU is charging and will provide more than 75% of the power required for 72 hours of operation. Flashing (fast): The BBU is charging and will provide less than 75% of the power required for 72 hours of operation. Off: The BBU dc output is unavailable.
Service/fault (amber)	Indicates that a fault condition has been detected within the battery backup unit.	Solid: A fault condition has been detected within the BBU and this resource requires service. Blinking: This resource has been identified by system management. Off: No known faults exist. This is the default state for this indicator.