I am trying to create a Mirrored RAID Set for my iMac I5 with 8 GB ram, which is running Mountain Lion, however, the prompt i get while in the RAID selection of the Disk Utilities window is "Creating a RAID set deletes all data on selected disk? How do I safely back up my data without erasing any of it? I am currently using two Western Digital 3 TB drives to accomplish this task.
Your help would be greatly appreciated.