MORE CLONE TESTING

TEST OBJECTIVE: To determine any further limitations to bootable clones and determine the true usefulness of a boot drive clone.

TEST SYSTEM CONFIGURATION:
  • M1 Mac mini, 16 GB memory, 500 GB Storage
  • MacOS 11.3 beta 5 (or 6 -- I have lost count)
  • Carbon Copy Cloner Version 5.1.26-b4 (6173)
  • Samsung X5 1TB Thunderbolt 3 SSD Samsung X5 500GB Thunderbolt 3 SSD


FINDINGS:
  • The only way to create a bootable clone requires allowing ASR to erase the target drive.
  • The System volume cannot be updated by any method and remain bootable.
  • Kernel Extensions -- as opposed to user extensions -- do not clone and have to be installed after cloning
  • The source volume security settings are not included in the clone, which inhibits installation of kernel extensions
  • I have been unsuccessful in all attempts to change the security settings of a cloned volume but I can easily change the security settings of an external drive that was created by the installer.
  • No matter how the external boot drive is created, whether by cloning or intalling the OS, the first time it is booted, all of the applications will be verified. (Given the 490,000+ files/items/objects in Xcode, it can take an annoyingly long time to verify just by itself).
  • Running a CCC clone to a previously cloned volume works (in this case CCC only clones the data volume), but all the applications must be re-verified the next time you boot from the volume
  • Apple's new 1 True Recovery Volume in macOS 11 (Big Sur) is a major improvement.
  • Compare volume structure of the internal drive with that of the cloned drive and a installed drive and you will see there are two containers (APFS partitions) iBootSystemContainer and RecoveryOSContainer, on the internal drive that do not appear on either of the external drives. Obviously the internal drive provides functionality that is not available on either of the external drives. I cannot verify this, but I have read that without these present in the system, the system is not bootable. (NOTE: this needs to be tested with a full macOS 11.3 installer when it is released, the results may be different.)
  • The Data volume on mounted external drives tend to unexpectedly dismount when not in use.


CONCLUSIONS:

  1. Bootable external Thunderbolt 3 or 4 SSDs are possible in macOS 11 M1 Macs running Big Sur.
  2. Those can be created either by installing or cloning from the internal drive.
  3. Any loss of contact with the "iBootSystemContainer" in the internal drive will render the system unbootable from any drive (this can be restored, but the process require using a second M1 Mac.)
  4. Clones are less functional than external drives created by installing from the Recovery Assistant, due to kernel extension and security policy issues.
  5. Bootable external boot drives are not as useful as they were in previous versions of macOS, but they are still viable.


FWIW — MY PERSONAL CHOICES:

  • Time Machine together with Apple's 1 True Recovery Drive remain my primary backup and disaster recovery tool set
  • I will continue to keep a copy of the latest full installer on a bootable thumb drive for deep disaster recovery purposes
  • For testing purposes I will install macOS on external drives rather than use clones because of limitations in clones.
  • I will continue to clone my data volume on the theory that in the event of a disaster, recovery might be faster than using Time Machine.
  • I remain eager to see Mike Bombich's "exciting new features" in Carbon Copy Cloner.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein