“You can define journaling file systems in many ways, but let’s
get right to the point. Journaling file systems are for people who
tire of watching the boot-time fsck, or file system consistency
check process. (Journaling file systems are also for anyone who
likes the idea of a fault-resilient file system.) When a system
using a traditional, non-journaling file system is improperly shut
down, the operating system detects this and performs a consistency
check using the fsck utility. This utility scans the file system
(which can take a considerable amount of time) and fixes any issues
that can be safely corrected. In some cases, the file system can be
in such bad shape that the operating system boots into single user
mode to allow the user to further the repair process.“So, now you know for whom journaling file systems were created,
but how do they obviate the need for fsck? In general, journaling
file systems avoid file system corruption by maintaining a
journal…”