Ok, I thought I would document and share the steps I took to install Mojave onto a RAID0 dual SSD setup that is bootable with APFS as the drive system. Some of you may be aware that the latest MacOS no longer supports booting from a RAID setup with APFS.
I give acknowledgement to the following two sources that I used to have success - mine is a variation of both:
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This specific post on MacRumors: Mojave on RAID with APFS - a HOWTO | MacRumors Forums
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This post from the Apple Developer Forums: https://forums.developer.apple.com/thread/108321
Okay, here we go.
What we need:
- Latest version of Carbon Copy Cloner (CCC) that can back up APFS in bootable form.
- Two SSDs of similar sizes to create the RAID0 single virtual drive.
- An external drive to clone your boot drive to.
- About 2-3 hours of time and lots of patience.
Step 1: Clone your OS boot drive from internal to external
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Make sure your boot drive is updated to the latest version of Mojave.
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Use CCC to clone a bootable copy of your OS drive to the external drive.
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To be safe, reboot holding down the left OPTION key, select the external drive, to confirm it can be booted and is working.
Step 2: Create the RAID0 drive
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Repeat, make sure both SSD drives have been backed up - this process will erase all data on them.
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Open up Terminal
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Enter this command:
diskutil list
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Find out the unique identifiers of each of your SSDs - they are their identifiers, and should be like disk2s2 and disk3s2 or something like that. Make sure you have the right drive identifiers!
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Once you are sure, enter this command to create the RAID0 array (use the correct drive identifiers below):
Diskutil appleRAID create stripe NameOfYourNewDrive APFS disk2s2 disk3s2
- Wait until this process finishes.
Step 3: Clone the OS boot drive from external back to internal
- Like Step 1 but in reverse - use CCC to clone the OS drive you backed up onto the newly created RAID0 volume.
Step 4: Boot up your new Mojave OS on RAID0 - you have to do this each time you restart.
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While rebooting, hold down COMMAND-S to boot in Single User Mode.
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Wait for all the text to scroll pass - once the command prompt for ROOT shows up (you may have to hit enter if you can’t see it), enter the following commands, pressing enter after each line:
/sbin/mount -uw /
touch /System/Library/Extensions/
exit
- The system will then boot up into Mojave successfully.
The advantages is that you are now running the latest MacOS on APFS on a RAID0, so you get speed.
The disadvantages are significant:
- You have to go into Single User Mode as per Step 4 above each time you restart
- You cannot update the system easily - to update, you need to do so via a cloned drive - clone the drive to an external bootable clone with CCC, boot into that drive, update it, and then clone that drive back to the internal RAID volume.
- This last disadvantage is a general risk for running a striped RAID0 array - you have faster speeds, but you trade that for greater risk of failure - there is no redundancy, so if one drive fails, the whole system fails, so make sure you have backups.
Hope this helps someone out there. Took me a couple of tries to work it all out.
I don’t do unencrypted drives anymore.