In order to create a RAID array, you'll need two disks (RAID 1) or at least two disks (RAID 0) that aren't already included in another RAID. If your LaCie 5big shipped with disks, you'll first need to delete the factory default RAID 0 array before you can create a new array (refer to Delete a RAID Array for instructions.

1. If your LaCie 5big shipped without disks, install them first (see Install Disks). Make sure the product is turned on and connect to your Mac as described in Get Connected.
2. Navigate to the Finder.
3. Go to the pulldown menu Go > Utilities.
   
4. The Utilities window will open. Click twice on the application Disk Utility.
5. Connected storage devices are listed on the left side of the Disk Utility window.
   
6. Click on one of the LaCie disks to see the action tabs. Click the RAID tab.
   
7. The RAID tab includes three important settings: RAID Set Name, Format, and RAID Type.
   
8. Clicking on the Format pulldown menu shows the file system formats available for the disks when creating the RAID. Select Mac OS Extended (Journaled).
   
9. Clicking on the RAID Type pulldown shows the available RAID configurations. See About RAID for information on the different RAID options.
   
10. Fill in a name for your Striped or Mirrored RAID Set in the field RAID Set Name.
    
11. Drag one of the disks to the empty field in the middle of the RAID tab.
    
12. Drag additional disks(s) to the same field in the middle of the RAID tab. Note that RAID 0 arrays can include two or more disks, while a RAID 1 array can only be composed of two disks.
    
13. To change the RAID Block Size, click the Options… button on bottom of the window. While this example shows the default, you may want to choose a higher RAID Block Size if you will be working with larger files (i.e. HD video and audio). Please see your audio/video software's user manual for the recommended RAID Block Size. Once you have chosen a RAID Block Size, click OK.
    
14. Click Create on the bottom of the window to begin building the RAID.
15. Click Create in the pop-up window.
16. Please be patient while Disk Utility configures the RAID. The RAID Set will appear on the desktop as a single drive icon.