Intel AXXRSBBU4 User Guide - Page 5

About the Intel® RAID Smart Battery Intel® RAID Controllers and Intel® Integrated Server RAID Modules provide reliability, high performance, and fault-tolerant disk subsystem management. A complete fault-tolerant strategy requires protection for all data, including the unwritten cached data in the RAM cache. If power is lost, the data in RAM is lost. To avoid this 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 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 RSBBUs provide an inexpensive alternative to using an uninterruptible power supply (UPS) or act as a second level of fault tolerance when used in conjunction with a UPS. The cache memory available on Intel controllers can improve 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 then 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 has been written to the storage device. This risk factor is eliminated when the Intel RAID controller has an onboard BBU. The Intel RSBBUs monitor 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 Intel RAID controller to the battery pack attached to the Intel RAID Smart Battery Backup Unit (RSBBU). As long as the voltage level stays below the predefined value, the Intel RSBBU provides power for memory. If the voltage level returns to an acceptable level, the RSBBU switches the power source back to the Intel RAID controller, and all pending writes to storage devices are completed with no data loss. A smart battery backup unit (BBU) 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 AXXRSBBU4 is a smart battery back up module using NiMH technology that is compatible with a backup auxiliary power source. Battery charging and recharging take place automatically. The AXXRSBBU4, which features NiMH battery cell technology, mounts directly to the following Intel® RAID Controllers using a small board-to-board connector (daughtercard): • Intel® RAID Controller SRCSATAWB • Intel® RAID Controller SRCSASRB • Intel® Server Platform S7000FC4UR SAS Riser Card • Intel® Server Platform SR1550ALSAS with LSISAS1078 ROC midplane • Intel® Server Platform SR2500ALLX with LSISAS1078 ROC midplane 1 Intel® RAID Smart Battery User's Guide