Edit: See this later post for a better solution. I've been able to get Mojave to install on to a RAID array of 4x 8GB USB sticks! The process is as follows: - Create RAID set using command line or disk utility. Format to HFS+ - Mount InstallESD from /path/to/beta/app/Contents/SharedSupport - Double Click on Packages/OSInstall.mpkg. Select the RAID array as target - The install will fail with an error, but don't worry: Code: system_installd: kextcache: /Volumes/Macintosh RAID: unrecognized /usr/standalone/bootcaches.plist; aborting - Code: cp -ap /Volumes/Macintosh\ RAID/usr/standalone/i386/boot.efi /Volumes/RAID/System/Library/CoreServices/ - Use Code: diskutil info /Volumes/Macintosh\ RAID to find the volume UUID and the booter volume: - Populate the booter volume using the above. Make sure to edit com.apple.boot.plist: - Reboot, and enjoy! Mine rebooted twice before it flicked through, but after that, no issues. I wasn't able to bless the volume, but I was able to choose it from the boot manager. Performance of array: One disk: Four disks in RAID: What I've learned: BUY BETTER USB STICKS! Now I just need to work on the installer process. If I can do that from the command time and update an existing install, I'll be happy. This was only testing with HFS+ and Mojave, but it should work with APFS and High Sierra with some tweaking.