A method that may include receiving, by a storage system, a write request for storing in the storage system multiple input data units that are related to a certain file; comparing, by the storage system, the multiple input data units to stored data units of the certain file to find matching and non-matching input data units; wherein each matching input data unit equals a corresponding stored data unit and each non-matching input data unit differs from a corresponding stored data unit; preventing a storage of each matching input data unit; storing each non-matching input data unit; and updating at least one storage system management data structure to reflect a reception of non-matching input data units while not reflecting a reception of matching input data units.