updated 10:15 am EST, Wed November 13, 2002
A new Knowledge Base article provides more details on ):
"Mac OS X Server version 10.2.2 provides a new journaling feature for the Mac OS Extended (HFS Plus) file system which enhances server availability and fault resilience. Journaling protects the integrity of the file system on Xserve and other computers using Mac OS X Server in the event of an unplanned shutdown or power failure. It also helps to maximize the uptime of servers and attached storage devices by dramatically expediting repairs to the affected volumes when the system restarts.
"Journaling is a technique that helps protect the integrity of the Mac OS Extended file systems on Mac OS X Server volumes. It both prevents a disk from getting into an inconsistent state and expedites disk repair if the server fails."