[Sticky] Mojave does not support booting from RAID volumes
Apple does not support booting from Apple RAID either.
You may be able to get it to work, but you cannot install security updates or other updates.
This is a problem that is not going away, as far as I know.
Using Mr. Collin's (dosdude1.com) software to install MacOS Mojave on unsupported Macs clearly overrides the restrictions Apple imposed on RAID solutions even on supported Macs. Once installed on a RAID of a supported Mac the behavior of the computer in respect to security or other updates is totally normal. This is the true solution also for hardware RAID using the Mavell controller, e. g. OWC Aura 2 resp. 4TB SSD.
Mr. Collin's software for MacOS Catilina does the same good job as far as I can see, so the near future shouldn't be an issue.
Dr. Hainich, aka Jaegermeister
Very nice, although I cannot refer users to hackintosh's for booting RAID volumes. We would try to support them, but there may be unanticipated issues.
And SoftRAID 6 will not be able to startup from any volumes at all, as we will be following driver guidelines for Catalina.
This is a messy area.
Apple engineering management seems to think RAID is unnecessary for their customers. Its being decided that Apple customers are not power users, do not use servers, mission critical work, etc. These power users are Apple's most loyal and vocal customers, unfortunately.
thanks for the replies, I think many users will do a combination of Carbon Copy Cloner (or alternative) and RAID on data storage.
Too bad, appears to be an attempt to get users over into iCloud storage to increase bottomline. Makes no functional sense to remove RAID booting support for any other reason. Follows lockstep dropping server line, dropping server software, except mobile devices. It is a troubling pattern from Apple management.
The main reason is Apple is 100% determined to prevent root based hacking/infiltration. Everything is being locked down. The team in charge of this project apparently does not care about its user impact (ease of installation, migrating, replicating systems, etc) they are tasked with locking down the OS.
This is what I believe is why RAID volumes can no longer boot. I have been told that it is going to become more difficult to create backup boot volumes as most users currently do. Cloud/snapshots, and other tricks will need to be used. Maybe a consideration was "since you cannot replace an SSD internally, if the internal fails, you need a new computer anyway", so why give users redundant startup capability?
The trick with to boot with an Apple RAID set up for Mojave (that is it) is to
1. set up the disks as HFS disks for Apple RAID.
2. Use CCC to clone the original boot disc in your iMac onto the Apple RAID. I use 8 of the 4TB Samsung SSD Evo 860 as my Apple Raid running through 2 of the OWC TB3 drives.
3. click on the Apple RAID as your start disk.
4. For security updates, boot in your original disk then copy the updated disk back onto the Apple RAID for boot from the Apple RAID.
P.S. You cannot do this with Catalina. I'm stuck with a 32TB SSD APPLE RAID 0 boot disk for a 2019 iMac (video rendering). I'm looking into the 2020 iMac with the 5700XT GPU and would like to have a RAID0 as a boot disk. If not, I guess I'm stuck with the PCI-e boot disk.