This article describes soft updates, their incorporation into the 4.4BSD fast file system, and the resulting effects on the system. We show that a disk-based file system using soft updates achieves memory-based file system performance while providing stronger integrity and security guarantees than most disk-based file systems. For workloads that frequently perform updates on metadata (such as creating and deleting files), this improves performance by more than a factor of two and up to a factor of 20 when compared to the conventional synchronous write approach and by 4-19% when compared to an aggressive write-ahead logging approach. In addition, soft updates can improve file system availability by relegating crash-recovery assistance (e.g., the }sck utility) to an optional and background role, reducing file system recovery time to less than one second