I just read this older hint about RAID and partitions on OS X Server, and it seems that it does not work in 10.4. So I tried doing it differently.
I opened Disk Utility from the utilities folder and did the following. On the two disks I would be using, I created equal partions, i.e. all the same size. I named these partitions 1a, 2a, 3a on the one drive, and 1b, 2b, 3b on the second. Then I went to the RAID tab and did this:
- Dragged the partions 1a and 1b to the RAID window and clicked Create.
- Dragged the partions 2a and 2b to the RAID window and clicked Create.
- Dragged the partions 3a and 3b to the RAID window and clicked Create.

