The purpose of the continuous media scrub is to detect and correct media errors to minimize the chance of storage system disruption due to a media error while a storage system is in degraded or reconstruction mode.
By default, Data ONTAP runs continuous background media scrubbing for media errors on all storage system disks. If a media error is found, Data ONTAP uses RAID to reconstruct the data and repairs the error.
Media scrubbing is a continuous background process. Therefore, you might observe disk LEDs blinking on an apparently idle storage system. You might also observe some CPU activity even when no user workload is present.