Apple Xserve RAID: Using RAID 1.2 Admin and Disk Utility - Manual (Page 23)

Chapter 2 Working With RAID Arrays 23
6 Choose a format for the array.
Note: You can take advantage of disk journaling by using the journaled volume format
in Mac OS X Server. Journaling is a technique that helps protect the integrity of HFS+
disks in RAID arrays. It limits the exposure for data loss and expedites repair if the
volume gets into an inconsistent state.
When you enable journaling on an array, a continuous record of changes to files on the
volume is maintained in the journal. If your system stops running because of a power
failure or some other problem, when you restart the system the journal is used to
restore the volume to a known good state. Although you may experience loss of user
data that was buffered at the time of the failure, the file system is returned to a
consistent state. In addition, restarting the system is much faster.
You can also turn journaling on or off for a volume at any time in the Information
section of Disk Utility.
7 Click Create.
Once you’ve created your RAID arrays, you can use RAID Admin to monitor the Xserve
RAID system.