During writing of the data checksums are created and stored. When read again, a new checksum is created and compared to the initial checksum. If incorrect, a checksum is created from another replica of the same data. After succesful comparison this replica is used to repair the corrupted replica in order to stay compliant with the configured protection level.
ReFS uses a background scrubber, which enables ReFS to validate infrequently accessed data. This scrubber periodically scans the volume, identifies latent corruptions, and proactively triggers a repair of any corrupt data. The data integrity scrubber can only validate file data for files where integrity streams is enabled. By default, the scrubber runs every four weeks, though this interval can be configured within Task Scheduler.
Integrity streams is an optional feature in ReFS that validates and maintains data integrity using checksums. Integrity streams can be enabled for individual files, directories, or the entire volume, and integrity stream settings can be toggled at any time. Additionally, integrity stream settings for files and directories are inherited from their parent directories. Once integrity streams is enabled, ReFS will create and maintain a checksum for the specified file(s) in that files metadata.
Though integrity streams provides greater data integrity for the system, it also incurs a performance cost.
Microsoft, S2D [SDS]/2019, Datacenter
Data Corruption Detection, Reads/Writes, Data Availability