Nikki, From my research (as in I really don't know this stuff, but I can [usually] cut & paste well enough).
Journaling:
It's a sort of file system record that is constantly updated with changes so that in the event of a crash the system can easily and quickly return the file system to the last good saved state. It was used only in OS 10.2 Server prior to Panthers release, but evidently Apple feels it's value is such that it should be used on the desktop version of Panther by default. You can read more about it in Knowledge Base Article No. 107249.
The big advantage here is that journaling all but eliminates the need to use fsck. If you have some really big volumes, like say a G5 with two 250 GB drives at two thirds capacity or a RAID array, think of how long it would take to run fsck on them when they crash. With a journaled volume you don’t need fsck, on restart it reverts to the last saved state. This makes for a huge time saver.
The journal file is not a replacement for the disk directory. It is simply a record of disk directory updates that have been created in RAM and are not yet written to the disk directory itself. The delay improves performance, and in order to safeguard the unwritten directory entries, they get recorded one after another in the journal file. If there is an improper shutdown, a routine named replay_journal reads from the journal file and updates the disk directory. You can see this happen if there is an improper shutdown, and you hold down Command V at the start of the next boot (this experiment should not be tried on a system lacking a backup).
So yes, I suppose it is best to keep journaling enabled.
Should this help, the real credit belongs to the contributors at MFI, from whom this was all lifted.
Hope this answers your questions, at least until the real experts arrive.
Harv
