Raid 0 on two SSDs on Macbook pro Mid 2012 (non retina) running Catalina?

Revision - it can be done with no cons.

I tried several methods since lesniakrafal did not work directly on my first attempt but after several attempts this does work. Please forgive if I stumble around, I have 25 years using unix but this is my first Mac I got 3 weeks ago.

1. I did try ccc and was not able to do updates or installs.
2. I did manage to install using unix style dd and seem to remember I could do updates, install problems can be overridden with xattr -cr or running csrutil disable from installation media. Problem was I had dd'd a 250GB drive to external 2TB with dd back resulted in a 250GB on a 500GB raid0 array. dd if=/dev/disk5 of=/dev/disk2 bs=64k where disk5 was the synthesized external install and disk2 was the (virtual raid). This might be useful if you want to copy your current install and possibly you could get updates to work normally using the method I present here after doing a resize.
3. Install to external drive, resize with diskutil apfs resizecontainer disk4s2 499400m, and dd back does work but again system updates and installs do not work without running csrutil disable from installation usb.
4. You can get a successful install on /dev/disk2 the virtual drive 2 ways. One using the Disk Utility to create the array and end up with a virtual container with no GPT or EFI partition. This runs but updates failed for me so diskutil list should show an EFI partition on disk2. Use lesniakrafal method with GPT assigned and EFI partition included on the raid0 array virtual drive, I did get a successful install with updates.
5. You do not need to download or install any patches, Catalina runs on this model. I give all credit to the following page/author where I leave out a few steps and embellish with some details of the install.

https://lesniakrafal.com/install-mac-os-catalina-raid-0/

1. Make a flash drive with Catalina installer.

   • Download with Safari/App Store with a Mac and insert a 16GB USB flash drive.
   • Open a terminal and type ls /Volumes to find the new flash drive, mine was /Volumes/NEW\ VOLUME
   • Run /Applications/Install\ macOS\ Catalina.app/Contents/Resources/creatinstallmedia --volume /Volumes/NEW\ VOLUME
   • Eject when done and reboot.

2. Hold down the option key and select the newly created flash/usb installer, you'll do this a lot.

3. Use the top menu bar to open a terminal.

4. Get a list of your current drives. diskutil list

5. Unmount the drives and destroy the gpt partitions. The internal drives were 0 & 1, 2 was the virtual raid, 3 was nested under 2, and I had the external drive were disk4 and disk5 not used in this example, and disk6 was the installer usb. diskutil unmountDisk disk0 diskutil unmountDisk disk1 diskutil unmountDisk disk2 diskutil unmountDisk disk3 diskutil unmountDisk disk4 diskutil unmountDisk disk5 gpt destroy /dev/disk0 gpt destroy /dev/disk1 gpt destroy /dev/disk4 (external disk)

Then follow lesniakrafal instructions

6. Setup the raid array which will have its own EFI partition. diskutil appleRAID create stripe Storage JHFS+ disk0 disk1 diskutil unmountDisk disk2 gpt create disk2 gpt add -t hfs disk2

7. Exit the terminal and open the disk utility and format the array APFS and named as APFS RAID

8. Exit the terminal and open the disk utility and format the external drive APFS if you are trying dd method.

9. Exit disk utility and install macOS Catalina. This time I got the option to install to the APFS RAID and the EXTERNAL DRIVE so did not follow the install to external dd back to internal method.

10. Install Catalina directly to the raid0 array.

11. Do not install any patches, Catalina will run on mid 2012 MacBook Pro.

12. Then it displays The bless tool was unable to set the current boot disk (we know how to fix that now from the dd attempts). Run the following commands. /sbin/mount -uw / mv /usr/standalone/bootcaches.plist /usr/standalone/bootcaches.bak csrutil disable

13. Sometimes there is a disk space low error popup just dismiss & Restart.

14. Installer resources were not found error, Restart and try again (maybe we don't know how to fix that). You may have to reboot several times and during my dd attempts and then one restart here I ran First Aid on the raid disks.

15. Restart to flash installer holding down option key not by automatic boot repair.

16. Run disk FirstAid on the raid drives if you haven't already.

17. Open a terminal and run the following commands again. /sbin/mount -uw / mv /usr/standalone/bootcaches.plist /usr/standalone/bootcaches.bak

18. Important!!!! Reboot and REMOVE INSTALLER FLASH so it only boots to the raid0 array. Then it booted into the new macOS and asks for location, language, Apple ID etc.

19. Reboot normally and Update 2021-007 10.15.7 and Safari.

20. Reboot. Error macOS can't be installed on your computer

21. Reboot with holding the OPTION KEY and flash installer again.

22. Open terminal and run these again. /sbin/mount -uw / mv /usr/standalone/bootcaches.plist /usr/standalone/bootcaches.bak

23. Reboot. Some updates could not be installed automatically. At first it was showed the 2021-007 update which changed to a Device Support Update.

24. Click Update Now. Your Mac is up to date, reboot and it is still up to date, and can install Firefox, woohoo!

25 Run the following commands as per lesniakrafal... sudo trimforce enable sudo update_dyld_shared_cache -root / (did not work for me)

26. Set root password and change to root account. sudo passwd root su - root

27. Final check and fixes from lesniakrafal diskutil list diskutil apfs updatePreboot disk3s5 diskutil apfs deleteVolume disk3s3

Everything works! Read speed 914MB/sec and write speed 844MB/sec