I upgraded from El Capitan to Catalina 10.15.5 on a MacbookPro mid-2012 , the oldest HW that Catalina will run on. Then, I created a RAID-1 drive using 2 USB disks. "About This Mac --> Storage" is not showing a logical 500-gb RAID-1 drive, the 500-gb disk RAID member, and the 500-gb partition RAID member is not displayed, but the 1-tb disk for this partition, and the other 500-gb partition on the same disk, is displayed.

On the other hand:
(1) "Go -> Utility -> Disk Utility ", (2) "Finder", and (3) command-line utilities all show the correct drive structure: the logical RAID-1 drive, the 2 physical disks, the 2 partitions of the 1-tb disk. Further, the amount of available drive space, on all disks, all agree.

I did a major reorg of my data when I upgraded to Catalina. My internal disk is SSD, and Catalina automatically formatted it to APFS. Next, I emptied the 500-gb and 1-tb disks into a 2-tb disk. I decided to re-format both (hfs+). Using Catalina's RAID tool, I created the RAID-1 drive.

Everything, except "About This Mac --> Storage", looks great so I am proceeding. So, I'm just reporting this and thinking this has something to do with a mid-2012 MacBook Pro being the oldest HW to support Catalina. Since data is critical to me these days, please tell me if I should be concerned about the strange "About This Mac --> Storage" result.

  • 2
    Creating a RAID arrary with USB disks is about the most unsafe (data wise) thing you can do. If the USB bus gets reset for any reason (and it does) you can suffer data loss. Also, by using a software based RAID setup (opposed to hardware), you’re piling extra work onto the CPU for management of the overhead.
    – Allan
    Nov 5, 2020 at 23:19
  • I believe that a RAID is a Redundant Array of Independent DISKS. I don't believe you can create a RAID where one (or more) member is a partition (which I think is what you are saying, correct me if I'm wrong) and @Allan is correct using the USB bus to create a RAID is not a great idea. You could buy a dual drive USB enclosure that way both disks will be on the same controller. Mar 6, 2021 at 0:47

1 Answer 1


About This Mac > Storage doesn't show my RAID set either, on my 2018 Mini running Mojave. I suspect it's just a bug in the OS.

  • Also running a 2018 mini with Mojave, no RAID set is shown. Jun 9, 2020 at 3:33

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