I've been running two software RAID-1 arrays on my OS X Lion Server for quite some time for backup and data storage purposes. At the time, I went for software RAID so that I didn't have to rely on any particular hardware. This worked great for me, but I've been thinking more and more that for my purposes, I did not need a RAID-1 array, what I needed was a separate, stand-alone offline mirror of my drives. This required me to break the RAID-1 arrays up into their individual volumes, this is how I did it.

I've already done my 'work' and 'backup' RAID sets, the last and the largest was the 'data' set. In Disk Utility, this is what it looked like. Two 2Tb disks.


Note: At this point, I did a full back up of the data, just in case something went wrong. I'd advise the same if you are going to try this.



With the RAID Set selected, I clicked one of the disks in the array. This selected the RAID slice for me.


Then, I clicked Delete and confirmed the option.


After a short pause, Disk Utility refreshed, the RAID Set was no longer there; the two individual disks were present as expected. Since this was a mirrored set, each of the volumes is an identical copy.


Then, I shut down, removed the 'spare' disk and booted up again, Disk Utility is showing just the one disk as expected.


A quick check of the disk showed no errors, success!


-i