Yes, you can. It's just not Apple supported. http://hints.macworld.com/article.php?story=20041013121106176
Article pasted below for posterity
Read the rest of the article for the how-to -- and please read the dislcaimer before you start doing something like this to your system! These instructions also assume some Terminal knowledge...]
DISCLAIMER: I take no responsibility if you choose to follow the steps below. I make no garauntees that this will work for you, however it did work beautifully for me. You may potentially lose all of your data, so I strongly suggest making a backup copy before trying this!
- Install a new hard drive
- Boot off Mac OS X Install CD #1
- Install a minimal OS on the new hard disk:
- Click 'Customize' when it asks what type of installation
- Uncheck everything but the BSD subsystem box
- This install takes maybe 10 minutes
- Reboot and hold the Option key to get the boot loader menu
- Boot off the new hard disk
- Open a terminal and
su
to root
- Run the following command:
diskutil list
:
- Look for the old disk in the output, will probably be disk1
- Next run diskutil enableRAID mirror disk1:
- The disk will disappear from the desktop for about 30 seconds, then re-appear
- At this point, I reboot the system and hold down Option while it reboots
- Now select the old disk to boot from
- Log in and open the Disk Utility app in Applications -> Utilities
- Select the RAID volume and the RAID tab
- Drag the new disk to the RAID
- Click Rebuild:
- Rebuilding usually take 1-2 hours depending on the size of your disk
- Drink a beer as you now have a mirrored boot drive
There should be an easier way to do this. You could theoretically boot into single user mode off of the Install CD, and bypass installing the OS on the new drive. However, diskutil
seems to be broken in single user mode; I believe this is a known bug.