A media scan is a background process that runs on all logical drives in the Storage Subsystem for which it has been enabled, providing error detection on the drive media. The advantage to enabling the media scan process is that the process can find media errors before they disrupt normal drive reads and writes. The media scan process scans all logical drive data to verify that it can be accessed, and optionally scans the logical drive redundancy
For more information, see Changing the Media Scan Duration.