Soft Updates

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In computer file systems, soft updates is an approach to maintaining disk integrity after a crash or power outage. They are an alternative to journaling file systems. Instead of duplicating metadata writes in a journal, soft updates work by properly ordering the metadata writes to guarantee consistency after a crash. Like journaling, soft updates do not guarantee that no data will be lost, but do make sure the filesystem is consistent. An advantage of a file system with soft updates is that it can be mounted immediately after a crash since there is no log replay. Soft updates were first introduced to FreeBSD by Marshall Kirk McKusick and are now available across the BSDs.