Apparatus and method in a cached raid controller utilizing a solid state backup device for improving data availability time

摘要

An apparatus for reducing data unavailability time after a loss of main power in a storage controller is described. The controller backs up its volatile memory containing posted-write data to a non-volatile memory upon detecting a loss of main power. The controller continues to provide battery power to the volatile memory to sustain the posted-write data. If the battery is able to supply power to the volatile memory until main power is restored, the controller foregoes restoring the posted-write data to the volatile memory from the non-volatile memory. By not incurring the restore time, which may be substantial if the volatile memory is large since read rates from volatile memories are typically slow, the data unavailability time is reduced. The selective restore feature is user-disableable and also includes a brown-out timer for allowing a user to specify how long to battery-power the volatile memory if the feature is enabled.