0xC9: New RAID Array

This week I got the family desktop configured to use a RAID array (mirrored) for primary storage. So now it's booting, mirrored, and I feel better knowing the data is safe. The array is built from two Seagate Barracuda SATA 7200.10 and I have a backup drive offline, waiting in its static bag in case one fails. They are 250 GB each to match the original size in order to avoid any mirroring issues and because they were inexpensive.

After setting it up, I did a disk verify on both the old and new volumes to see which one was faster. The old volume could be verified in about 10 minutes. The new one took almost 2 minutes. So I'm very happy with that boost.

I didn't need any special software to do this. All I used were the utilities and features supplied in Mac OS X 10.5 Leopard. I've seen several approaches, some more risky than others. Some suggest third party software to accomplish what Leopard can already do. So I recommend the following procedure:

Install the new drive.
Boot and begin in the Disk Utility to erase the new drive, calling it "New Macintosh HD".

Quit Disk Utility and issue a terminal command:

diskutil enableRAID mirror /Volumes/New\ Macintosh\ HD

Reopen the Disk Utility, click on the new drive, and use the Restore option to copy the boot disk onto "New Macintosh HD".

You will need to pay attention because the new drive has two entries in the list of volumes; slice name and RAID group name. You want to ignore the slice.
In the Restore tab of the new drive, drag the old volume to the first field and the new volume to the second field. This will cause the first field to become "/" and the second field to become "New Macintosh HD" with an icon.

When the copy is complete, selected "New Macintosh HD" as the boot disk in System Preferences and reboot.
Now verify the old drive to make sure there were no errors. I recommend doing this after booting on the new drive because the verify can now be more thorough due to the fact that the system didn't boot to it. If it's all clear, proceed. If not, you're on your own. You probably just need to do a repair and this procedure start over. Make sure you boot back to the old drive after the repair.
Shut down and remove the old drive and replace it with another identical drive.

Replacing it is optional, but the old drive is now a backup of the system. In my case, I wanted both drives to be identical for performance reasons.
Boot into the one-disk (degraded) RAID group and use the Disk Utility to drag the new disk into the RAID group. This erased the new disk and start the mirror "repair". This may take many hours to complete.
You need to pay attention because the dialog window in the Disk Utility can be behind the main Disk Utility window. If you lose it, click Window, then Disk Utility Progress. If it stops, close the Disk Utility and open it up again. If you get bored, open the Activity Monitor and watch the Disk Activity or go have a beer (preferably both).

This is only one of many possible solutions. Using this as the most basic solution is great because it guards against failure and is very low maintenance once it's set up and it doesn't cost as much. Apple's Time Machine is still my favorite solution, but it's pretty expensive to do it right.