M1 MacOS no longer allows external startup boot drives?

I have a Mac Mini M1 and a MBA M1 both running 12.3. I have no issue making a bootable clone using CCC. They show up in the start up menu. When booting from them they will state that authorization is required. Usually entering my PW works but sometimes it is rejected. In that case just select continue without authorization and it will boot anyway. I only use Thundebolt drives as USB drives appear more problematic.

Does my CCC backup have to be bootable for me to restore data from it?

No, in fact we no longer recommend that you attempt to make your backup bootable. Bootability is a convenience that allows you to continue working if your startup disk fails, but it is not required for restoring data from a CCC backup. You can restore individual folders and older versions of files (i.e. from snapshots) using CCC while booted from your production startup disk. CCC backups are also compatible with Migration Assistant, so you can use Migration Assistant to restore all of your data to a clean installation of macOS (e.g. on a replacement disk).

As discussed here

on an M1, can a 2.5" SSD serve as an external boot drive?

with 12.3.1 I created a bootable SATA III SSD in a Thunderbolt 2 enclosure connected to my Studio Max via Thunderbolt 3/4>2 adopter. It boots fine but boot up is slow

I was told that the drive needs to support Thunderbolt 3 to allow boot up capability. I’ve successfully used a Samsung X5 SSD drive fairly recently with my M1 Mac.

M1 macs work with bootable external drive with 12.3. I have not updated to 12.3.1 so I cannot speak to that one.

There has been something changes since Monterey 12.3 or 12.3.1 where attempting to Install to External Drive a full version may or may not work.

The, even is successful - Broken Monterey System Volume Seal

Judging from the comments from link in earlier posting, one or more users seemed to have more success booting to External Drive of Monterey with a lower version of macOS 12

Even attempting to make a Legacy Clone via CCC is not longer suggested by users and the Developers of CCC

The " Walled Gardens of Eden ( Apple ) " have gotten higher and higher with each new versions of macOS.

CheviotView wrote:

I believe it is still possible to create a bootable macOS installer on a USB stick with Monterey?

It is. Apple explicitly supports this: How to create a bootable installer for macOS - Apple Support

But Apple does say:

These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.

Useful presumably if you somehow accidentally wipe or corrupt your internal drive (assuming that’s possible now).

This would be a job for internet recovery.

The topic at hand is how to permanently boot a Mac from an internal hard drive. It reminds me of the old Comcast "Slowskys" advertising campaign. A couple of sentient turtles use DSL instead of Comcast cable internet because DSL is so much slower. See https://www.youtube.com/watch?v=NR7oZqgFA-0

I can answer one technical question however. External thunderbolt drives are not like external USB drives. The differences are more than just the cable. Internally, USB drives are attached to the USB bus. In addition to limiting their speed, this limits the metadata, such as SMART statistics, that can be communicated with the disk. Sometimes the operating can't even tell if an external USB drive is an SSD or not.

But to the operating system, Thunderbolt drives are the same as internal drives. Although the Thunderbolt bus is still slower than internal connections, it is faster than even then fastest SSDs. The Thunderbolt bus support all drive metadata. In fact, when I query for SATA or NVMe drives inside EtreCheck, it returns Thunderbolt drives along with internal drives. I have to do extra work to identify Thunderbolt drives as being external. Therefore, it makes a lot of sense to be able to boot more easily with an external Thunderbolt drive.

There are some inexpensive Thunderbolt 3 SSDs available. These are bus-powered M.2 SSDs. They are often sealed devices that aren't any more expandable than the internal drive. There are also some very expensive Thunderbolt RAID devices marketed to the professional market. But in between, those super-expandable and inexpensive devices are all USB, and marketed to the PC market. They can be used for external storage, Time Machine backups, but external booting is going to be slow, problematic, and generally painful.

I use SuperDuper:

https://www.shirt-pocket.com/blog/

Birck Cox wrote:

That seems to be the case. I've been struggling for a week to create a second, external boot disc for my M1 Mini, without success.

How to start up your M1 Mac from an external drive | Macworld

Birck Cox wrote:

If a damaged drive were the only circumstances necessitating an alternate boot drive, that would suffice, but there are other reasons for wanting an alternate drive.

That was a big deal back in the years of mechanical hard drives. Modern SSDs are much more reliable. Modern Apple SSDS are up to 100 times faster than a mechanical hard drive. With iCloud and modern Time Machine, your data is even safe from accidental deletion. There is no reason for most users to ever use an external boot drive.

Apparently that option is no longer available on M1 Macs.

It is an option, but it is an advanced option. Macs are consumer computers. Those few reasons for having an external boot drive are advanced operations. Most users don't need that. One of the biggest problems with macOS is all these decades of Unix history that makes the system more complicated.

I use Carbon Copy Cloner (CCC) and pick legacy format to make it bootable. I have no issue as stated. With the intel Mac if your internal drive failed I could boot from the external but with M1 Mac if the internal drive fails you can no longer use the external. I use CCC mostly to backup my data only

Birck Cox wrote:

Why would usability of an external drive depend on the viability of the internal drive?

There aren't any separate components. If the internal drive has actually failed, then it is extremely unlikely that the computer will boot with any external storage.

But it doesn't tell me why Apple would choose to make internal disc failure a complete dead end for the computer.

It is not a question of choice. Apple would have to design the computer from the ground up to be able to handle internal storage failure. But that kind of failure is so astronomically unlikely that the extra time and expense required would be a waste to Apple and to end users who would have to pay for it.

The internal drive of a Mini M1 is, theoretically, "soldered in", so replacing that drive would mean either junking the computer or, at the very least, taking it to the Apple Store and paying for repairs.

The internal storage on the Mini M1 is most definitely soldered in. The Mac Studio does have replaceable storage, but it uses a proprietary connector. There are reports that people have successfully swapped identical storage chips, but they haven't been able to upgrade it.

Just ran another test. After updating my M1 to 12.3.1 I attempted to boot my external that had 12.3 OS. It would not boot and locked up the Mac. After a hard power restart there was a log lag then it booted up on the external slowly. I do not like this process any longer so I believe no more external boot drives for now.