KB article explains how Data ONTAP responds when a medium error occurs during a disk reconstruction. Media scrub is proactive reading of all the disks to detect and fix media errors before they cause ...KB article explains how Data ONTAP responds when a medium error occurs during a disk reconstruction. Media scrub is proactive reading of all the disks to detect and fix media errors before they cause issues during reconstruction or double errors. Although, this significantly reduces the number of issues caused by such errors, it cannot prevent all the errors.