My Leopard installation used a OS X RAID 0 implementation to keep my system safe and sound. I mirrored two 1 TB drives then used them for my startup volume. Â When I switched to Snow Leopard, I needed an extra drive to ensure I had sufficient backups prior to installation (I always clean install when I upgrade operating systems.)
I thought the easiest thing to do would be to “split” the RAID 0 drives up with both containing a complete backup of my Leopard installation. But I also thought it sounded too easy and while purchasing Snow Leopard at the Apple store, I casually asked “can you split a mirrored RAID and retain the data?”
“No” was the response by two of Apple’s finest.
Still it seemed worth it to try it. Particularly when Disk Utility actually states (something to the effect) “when deleting a RAID configuration, you’ll end up with two drives containing identical data”. WOW! That is exactly what I want, where do I click?
Clicking on “Delete”, I waited and voila! Â A message informing me that the “Operation can’t be performed because the RAID configuration can’t be unmounted.”
“Mmmmmm. That should be easy to fix, perhaps Finder is still “using” the drive.” Close all windows, try again.
“nope.”
Eject RAID?
“Nope”
Reboot? “Nope”
Use diskutil instead of Disk Utility? “Nope”
Finally, what if  I booted in SAFE Mode? Ejected the drive, then deleted?
Bands played in the street, everyone rejoiced, the skies cleared and the sun shone brightly! “It worked!”
So here’s the deal. To split a Mirrored RAID 0 configuration into two identical drives:
- Boot in Safe Mode
- Eject the RAID volume
- Delete the RAID configuration in Disk Utility
Now back to installing Snow Leopard…