MediaScan’s role within the file system protection framework is to periodically check for and resolve drive bit errors across the cluster. This proactive data integrity approach helps guard against a phenomenon known as “bit rot,” and the resulting specter of hardware-induced silent data corruption.
MediaScan runs as a LOW impact, low-priority background process, based on a predefined schedule (monthly, by default).
First, MediaScan’s search and repair phase checks the disk sectors across all the drives in a cluster. Where necessary, MediaScan uses the OneFS dynamic sector repair (DSR) process to resolve any ECC sector errors that it encounters. For any ECC errors that cannot immediately be repaired, MediaScan first tries to read the disk sector again several times in case the issue is transient and the drive can recover. Failing that, MediaScan attempts to restripe files away from irreparable ECCs. Finally, the MediaScan summary phase generates a report of the ECC errors that were found and corrected.