If you prefer to stick with Terminal, you can run the diskutil command to identify your Mac’s disk numbers. In our case, our SSDs are disk2 and disk3. With the disk selected, find the Device box on the right side of the screen and note the disk number. In our example, we’re using two Samsung 840 EVO SSDs, so we’ll select one of the disks, not volumes, from the Disk Utility sidebar on the left. Looking at GUI method first, launch Disk Utility and select the first disk that is destined for your RAID volume. We can obtain this information in one of two ways: via Disk Utility or via the diskutil command line function. To illustrate how users can manage RAID volumes in OS X El Capitan, we’ll use an example in which we want to create a 2TB RAID 0 volume from two 1TB SSDs, labeled TB1 and TB2. The first step is to determine the disk number of each drive you wish to include in your RAID, as we’ll need this information for the Terminal command that will eventually create the RAID volume.
The process isn’t as simple as the old Disk Utility GUI, but for users running Apple’s latest desktop operating system, it’s the next best thing to investing in third party software SoftRAID.
While El Capitan’s version of Disk Utility may be missing this important feature, the good news is that users can still perform many RAID functions via Terminal.
