34 Planning: RAID Controller ModulesRAID Controller Module—Additional FeaturesBattery Backup UnitEach RAID controller contains a two-cell Lithium ion nanopolymer batterybackup unit (BBU). It provides power to the RAID controller module in theevent of a power outage. For information on removing and installing the BBU,see "RAID Controller Module Backup Battery Unit" on page 224.NOTE: For virtual disks, the RAID controller firmware changes the data cachesetting based on the state of the battery. If the battery is missing or does not havesufficient charge, the controller flushes the cache and sets the write cacheattribute to Write Through for all virtual disks. When the battery is replaced, WriteBack is re-enabled.Storage Array Thermal ShutdownThe system automatically shuts down when system temperature exceeds thesafe threshold. The battery backup unit protects against data loss byproviding power to offload to non-volatile memory in the event of power loss.It is not necessary to shut down any MD1200 Series expansion enclosuresattached to the storage array when thermal shutdown occurs.Temperature threshold values determine the temperature at which shutdownoccurs. These thresholds cannot be changed.18 Management portspeed LEDLights green when ethernet connection is operating at1000 Mbps.Lights amber when ethernet connection is operatingat 100 Mbps.Off when ethernet connection is operating at 10 Mbpsor is not active.19 Management portactivity LEDLights green when ethernet connection is active.Off when ethernet connection is not active.Item Component Function
