Intel RMS25PB080 Hardware User's Guide - Page 13

1 About the Intel® RAID Smart Battery AXXRSBBU9 Intel® RAID (Redundant Array of Inexpensive Disks) Controllers and Intel® Integrated RAID Modules provide reliability, high performance, and fault-tolerant disk subsystem management. A complete fault-tolerant strategy requires protection of all data, including the unwritten cached data in the RAM cache. If power is lost, the data in the RAM cache is lost. To avoid data loss, a battery can be added to supply power to the RAID RAM during an AC power outage or if the AC power cord is removed. A battery backup unit (BBU) protects the integrity of the cached data on Intel® RAID Controllers by providing backup power if there is a complete AC power failure or a brief power outage. The Intel® RAID Smart Battery Backup Unit provides an inexpensive alternative to using an uninterruptible power supply (UPS) or it can act as a second level of fault tolerance when used with a UPS. The cache memory available on Intel® RAID controllers can improve the overall system performance. Writing data to the controller's cache memory is much faster than writing it to a storage device. Write operations appear to complete very quickly at the software application level. The Intel® RAID Controller writes the cached data to the storage device when system activity is low or when the cache is getting full. The risk of using write-back cache is that the cached data can be lost if the AC power fails before it is written to the storage device. This risk factor is eliminated when the Intel® RAID Controller has a BBU installed. The Intel® RAID Smart Battery Backup Unit monitors the voltage level of the DRAM modules installed on the Intel® RAID Controller. If the voltage drops below a predefined level, the battery backup module switches the memory power source from the controller to the battery pack attached to the Intel® RAID Smart Battery Backup Unit. As long as the voltage level stays below the predefined value, the battery backup module provides power for memory. When the voltage level returns to an acceptable level, the module switches the power source back to the Intel® RAID Controller, and all pending writes to storage devices are completed without losing any data. The battery backup module has built-in functionality to charge the battery pack automatically and to communicate battery status information such as voltage, temperature, and current to the host computer system. The Intel® RAID Smart Battery AXXRSBBU9 is a smart battery backup module and uses lithium-ion (Li-Ion) battery technology. It is compatible with a backup auxiliary power source. The battery is charged automatically. Intel® RAID Smart Battery AXXRSBBU9 User's Guide 1