29.5 An Overview of Journaled File Systems

A journaling filesystem keeps a journal or log of the changes that are being made to the filesystem during disk writing that can be used to rapidly reconstruct corruptions that may occur due to events such as a system crash or power outage.

There are a number of advantages to using a journaling file system. Both the size and volume of data stored on disk drives has grown exponentially over the years. The problem with a non-journaled file system is that following a crash the fsck (filesystem consistency check) utility has to be run. The fsck utility will scan the entire filesystem validating all entries and making sure that blocks are allocated and referenced correctly. If it finds a corrupt entry it will attempt to fix the problem. The issues here are two-fold. First, the fsck utility will not always be able to repair damage and you will end up with data in the lost+found directory. This is data that was being used by an application but...