Cause: One or both of the members of the mirrored volume has failed, and the volume is no longer fault tolerant. To avoid data loss, you should attempt to repair the volume as soon as possible.
Solution: If the dynamic disk's status is Offline or Missing (it cannot be accessed at all), an icon (X) appears in the graphical view of the Missing or Offline disk. For instructions describing how to repair the mirrored volume, see Reconnect the disk and repair the mirrored volume.
If the disk's status is Online (Errors), an icon (!) appears in the graphical view of the disk. For instructions describing how to reactivate the disk, see Reactivate a mirrored volume.