If it's still a new install, and you don't mind installing again, just restart the installer. Once you make the language selection, wait for 2-3 seconds and the menu bar should appear. Under the Utilities menu is Disk Utility which will allow you to set up a RAID array.
Be warned however, software arrays can be a bit unreliable. I had a Mac Mini come to me at work one time, where somehow or another the RAID array just flat out refused to deactivate. Even using Unix level commands at the terminal from the install disc. I had to open the thing up, disconnect one of the drives, format the one still connected, then go back and do the same for the other drive. So, maybe take a little time to think about whether or not you REALLY want a RAID array, and whether or not it will really benefit what you want to do in any way.
Hi,
I have a new MAC OS X Server using 10.6. Built it but then realised that it hadnt setup any RAID configuration. It has two disks that are the same size and a controller card but when I installed the OS it never prompted me for a RAID configuration.
Any ideas.

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