HP Surestore Disk Array 12h - And FC60, Advanced User'S Manual, Page: 45 / 466

Array Controller Enclosure Components
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Battery Backup Unit
The controller enclosure contains one removable battery backup unit (BBU) that houses
two rechargeable internal batteries (A and B) and a battery charger board. The BBU plugs
into the front of the controller enclosure where it provides backup power to the
controller’s cache memory during a power outage. The BBU will supply power to the
controllers for up to five days (120 hrs). All data stored in memory will be preserved as long
as the BBU supplies power. When power to the disk array is restored, the cache data will
be written to disk.
Figure 16
Battery Backup Unit
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During a power outage, do not remove the controller or the BBU. Removing
either of these modules can compromise data integrity.