What should I do when I see a
      RAID-5 data storage subsystem fault warning?

Our Answer:

Never ignore a RAID-5 data storage subsystem fault warning, or any behavioral anomaly.  If a drive has failed, conceptually, the first response recommended consists of three steps:  back up the data in the array, then replace the drive, and then rebuild.  Even though your data remains completely available, a warning typically means that the system is running in a degraded mode: the fault tolerance is lost immediately when one drive malfunctions.  Your goal is to limit your RAID degradation or loss of fault tolerance to the shortest reasonable time.