Every few seconds, NTFS checks the cache to determine the status of the lazy writer and marks the status as a checkpoint in the log. If the system crashes subsequent to that checkpoint, the system knows to back up to that checkpoint for recovery. This method provides for more expedient recovery times by saving the amount of queries that are required during recovery.
Note This level of recoverability protects metadata. User data can still be corrupted in the case of power and/or system failure.