By definition...
"A journaling file system is a fault-resilient
file system in which data integrity is ensured
because updates to directories and bitmaps are
constantly written to a serial log on disk
before the original disk log is updated. In the
event of a system failure, a full journaling
filesystem ensures that the data on the disk has
been restored to its pre-crash configuration.
It also recovers unsaved data and stores it in
the location where it would have gone if the
computer had not crashed, making it an important
feature for mission-critical applications."
For additional info (one I like very much)
take a look at IBM's JFS for Linux...
http://oss.software.ibm.com/develope...one=opensource
