Using an External SSD as a Startup Drive

Hi Tidbits

I have been struggling with this effort for the last 48b hours.

I have a external Samsung 2GB SSD T7 connected to a 2022 MBP M2 running OS Ventura 13.4.1

I recently figured out that my Carbon Copy Cloner backups on both of my 2GB SSD T5 drives connected to a 2022 MBP M2 running OS Ventura 13.4.1 cannot be used as an external startup drive. ( Ideally would like to know how I can make them act as one but that is a question for another day.)

I have a stand alone “InstallAssistant.pkg” for OS 13.4.1n my applications ƒ.

I initially formatted the T7 as an AFPS drive and ran the InstallAssistant.pkg.

It installed “something” on the T7 and told me to restart.

The MBP restarted on its internal hard drive.

I tried to force the MBP to startup on the SSD via the startup disk option in System Pref (general) but it said there was an error.

I shutdown and started the MBP, holding the power button down until the startup options appeared.
The SSD was there but when I selected it and went to continue, nothing happened.

I then erased the SSD, and used the option to install a pristine copy of OS Ventura using the recovery screen on to the SSD via a web download.

I could not still get the MBP to recognize the SSD an a startup disk.

I then formatted the SSD as a MacOS Extended disk and used the InstallAssistant.pkg to install the system files.

I could not still get the MBP to recognize the SSD an a startup disk.

I then erased the disc, leaving it formatted as a MacOS Extended disc and using CCC, backuped my internal drive to the SSD.

I could not still get the MBP to recognize the SSD an a startup disk.

The T7 SSD is not encrypted. My internal SSD is “fileVaulted.”

The two T5 SSDs are also “file vaulted” and I presume that is why they cannot be used as an external startup disk.
They both are formatted as AFPS disks

So, after two days, and meekly bowing my head in failure, I thought I would ask you for help.

I have searched on line, and even found a set of terminal commands from a MacWorld article that supposedly would allow me to create an external Startup disc BUT the terminal command “createimage” is no longer recognized by Terminal…

I even found a OS Ventura version 13.0.1 DMG file that I thought might work but I get the same results independent on how the T7 SSD is formatted.

My guess it I am doing something wrong.

I just cannot figure it out.

My tail is between my legs. This problem has beaten me.

May I ask for some guidance, please?



Have you tried the steps in these articles by Howard Oakley?


FileVault does not prevent you from booting. In fact, the default is FileVault is turned on for the internal disk that is used to boot any new Mac these days.

What does prevent you from booting is that you can no longer just boot externally from a disk with any existing macOS install on it like you used to. The disk needs to be set up in a specific manner and with a bootable system linked to the admin user of the system you want to boot (“ownership”). That is why we can no longer just hook up another Mac’s disk and boot from that. However, there are ways to still get macOS onto an external disk and boot from that. You just need to go through the Installer. Howard Oakley’s excellent guides to which @josehill linked above tell you exactly how to do it.

In addition to Howard Oakley’s most excellent articles, you might want to take a look at Joe Kissel’s also most excellent e-book “Take Control of Backing Up Your Mac” Take Control of Backing Up Your Mac – Take Control Books

Especially if you’re looking to use that external drive as a bootable backup as there are chapters in the book specifically geared to not only creating but updating a bootable backup on an external drive.

You should also realize that an unlike an Intel Mac, an external drive can not be used to boot an Apple Silicon Mac should its internal hard drive completely fail. Bootable external drives are not the panacea that they used to be.


This is true and it is a shame. That used to be a really nice Mac thing.

But I think it’s also fair to point out that on Apple Silicon Macs the internal “drive” is flash memory with Apple’s very own flash memory controller embedded in the AS SoC and that instances where the internal flash memory fails such that you can’t boot the Mac at all, not even in recovery (i.e. flash has failed to the point where the Mac can’t get to its “firmware”, which unlike on Intel Macs actually resides on the internal flash storage), are very, very rare.

If the flash is just corrupted, you can use any other Mac with USB-C ports (even Intel will do) and use Apple’s free Configurator 2 to rebuild the partitions on its flash storage and install proper “firmware” in DFU mode. If the flash storage itself has actually failed, you’ll need to have the board swapped anyway. But again, it is very rare for this to occur. So while missing that old Mac feature is indeed a bummer, you could argue it’s tradeoff in many cases worth taking.

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Good point and true indeed. That’s the major reason why I said that the bootable external drive isn’t as much of a panacea for system recovery as it used to be. System recovery scenarios need to be re-thought in light of the system disk layouts of Monterey+ and the architectural changes to the boot process on Apple Silicon.

My irritation with not being able to do these external boots aren’t so much related to backups.

We frequently used clones booted on other machines to test various updates. We could clone an existing server for instance, run an update to the OS and Server app and then test that everything worked as expected.

We could even leave it running for several days and test it in production. If everything passed we’d clone it back to our server.

It was a step we took with many of our critical system updates. Of course it was also reassuring we could boot a broken system from a running clone.

I HATE that apple has taken this away.



Thank you for the links.

I will try today to create a bootable Mac and let the list know the outcome.
Thanks again

Dear All,

I followed the directions in the article “Make a Ventura bootable external disk for an Apple silicon Mac – The Eclectic Light Company” I downloaded from the App Store a copy of OS Ventura. I then installed it per the article. The Mac restarted twice, but came back on the internal drive. I held down the power button to boot into recovery mode and selected the external drive. The icon was highlighted, the spinning disc happened for a second, and then nothing. Rebooted off the internal drive and looked at what was on the external drive. Even though I selected it, my admin account was not on the external drive.

When I went to try to install Ventual again, the following came up:

Some differences between the article and me:

I am using a factory fresh Samsung t-7 2 TB drive (blue if that makes a difference.)
I am using the USB C 3.2 version cable that Samsung sent with the drive.

I have no clue what a thunderbolt cable is but I am willing to buy one if people think that may be the root cause of the issue.

I have a MB Air M2/Ventura. After unsuccessfully trying to boot a clone from an external HD, I learned that the external drive needs to have a Thunderbolt connection to be bootable. I got an Envoy Express from OWC and fitted it with a 1 TB Aura P12 Pro. Then, I first make a clone with SuperDuper!, after that, I installed OS Ventura on that volume, then I had to allow that drive to boot, administrator privileges, and a little back and forth, but it finally works, and booting from that is almost as fast as from the internal drive.

HI! Does this mean that you think that just buying a thunderbolt cable is not enough to get the Samsung T7 to boot?

I’m not sure, but I suspect the drive has to be fast, too. I see that the Samsung T7 says USB 3.2 Gen2, which is slower than Thunderbolt. I don’t know whether just connecting with the faster cable will make the whole shebang fast enough, but I wouldn’t bet on it. Maybe somebody here, or Samsung themselves, could answer that.

The T7 is not a TB drive. Its interface is regular USB-C 3.2 Gen 2 so if you have a decent 3.2 cable that should not be the problem. But I will say that this is not the first time users have reported trouble with these Samsung all-in-one drives on Macs.


I’ve read that it should be possible to boot from a USB 3 drive, but at some earlier point, the external had to be a Thunderbolt drive. When I got an M1 Mini, I also bought a Sabrent TB enclosure because I knew I was going to want to boot from an external drive running Monterey.

Sabrent TB3

I installed a Samsung 970 EVO Plus NVME drive, and was able to get everything working by booting from a Monterey installer on a flash drive that I had prepared.

970 EVO Plus

At some point in the process, I had to indicate that I was the “owner” of the system on the external. IIRC I migrated an account from another drive. After all that, I have a working Monterey drive that I’m using as my boot drive.

Dear All, Thank you for all of your help. I have come to conclude that there is no way to make a SamSung T7 external SSD into a startup drive. I tried with the Samsung provided USB C cable as well as a thunderbolt 4 cable. From the tread, if I want to make this work, I need to buy a thunderbolt 3 or 4 enclosure and some internal SSD drive. What I was HOPING to find was a bundle that included a Thunderbolt 4 enclosure and a 4 TB internal SSD card that the seller ABSOLUTELY guaranteed to work as a startup drive on an M2 Mac. OWC makes a TB 3 enclosure with 4 TBytes. I would prefer to have a TB 4 enclosure only because I do not buy often and am thinking toward the future.

If someone has actual experience with a 2 or 4 TB Thunderbolt 4 enclosure that can act as a startup drive, please let me know. I have read the comments and THINK I have seen something like this but need to be more comfortable as I am shipping this far far from the USA.

Again, sorry if I am asking for a person or two to repost their actual real word experience. I just need to be 110% sure. Lee

As I wrote above, I have an OWC Envoy Express (which is TB3) fitted with a 1 TB (they come prefitted up to 8 TB) Aura P12 Pro. I can boot from it reliably, it’s fast as blazes. They have other Envoy models which are even faster, all TB3. I don’t see anything there with TB4. I’ve been using their stuff for decades, always well advised, always satisfied. If TB4 is so important for you, you could ask them about it. (BTW, I’m in the EU. OWC can ship from here, so I needn’t pay customs duty.)

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I don’t think there is a performance difference for external disks between TB3 and TB4. They both have maximum bandwidth of 40 Gb/s.

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Let me attempt to clear up a couple things here.

You can definitely boot an M1/2 Mac on Ventura with a USB-attached SSD. You’d want to make sure it’s a combo that actually supports the full 10 Gbps available to that bus on a Mac. This for example is such a combo and at $70+$13 for 2TB it’s very inexpensive.

There is no difference (in terms of performance of the attached disk) between TB3 and TB4. You can in fact not even get close to the promised 40 Gbps (or roughly 3.2 GB/s accounting for overhead) on any Mac. The very best rates you’ll see are about 2.8 GB/s (read) and 2.1 GB/s (write). So that inexpensive NVMe flash stick above will be more than adequate to fully saturate any Mac’s TB abilities. An inexpensive TB3 case would be this one, but there’s another good one with removable cable for $10 more and you can of course get fancy if you like (it’s $140 but it does have a very good rep).

There is definitely a performance advantage from going TB3 vs.10 Gbps USB-C. When booting a Mac it’s more about IOPS than raw b/w though so the advantage will be palpable, but not to scale with what you’d expect from ~1 GB/s → 2.8 GB/s.

Also, if you’re booting a Mac, you do NOT want to use any SATA-interfaced SSD. You’re going to see 400 MB/s at best and boot time is going to be at least twice as long as on an inexpensive USB/NVMe combo such as the one I listed above. In fact, these days chances are NVMe flash is going to be less expensive at 2TB than quality SATA SSDs despite it’s clear performance advantage (SATA capped at 6 Gbps).

And finally, once again, I can only suggest people leave their hands off ready-made all-in-one solutions and instead buy quality flash and enclosures separate, according to their needs, and from brands or using models with a reputation to work reliably. The 2TB TB3 solution here is $170, will max out the Mac’s TB bus, and boot any AS Mac just fine. There’s very little that you could argue against going such a route. Just keep in mind, it still stands not a chance against the Mac’s internal flash (up to ~ 7GB/s), alas, upgrading that is just not available to users.


TB3 and TB4 have identical bit-rates and physical connector. (maximum 40 Gbit/s over a USB-C connector). Most of of the differences between the two is that many features optional in TB3 are mandatory in TB4.

The differences are:

  • Minimum bandwidth available for data: 32 Gbps for TB4, v.s. 16 Gbps for TB3. In both cases, devices might be able to provide more, but they aren’t required to do so. Bandwidth beyond the data limit may be used for video.
  • Video: Up to two 4K displays or one 8K display for TB4 vs. one 4K display for TB3.
  • Topology: TB4 supports up to four TB ports - one upstream and three downstream, supporting tree-like topologies. vs. TB3 only supporting two (one up, one down, supporting daisy-chain topologies).
  • Laptop charging: TB4 mandates up to 100W on at least one port. Optional for TB3 (which only requires up to 15W on all ports).
  • Wake-from-sleep: TB4 requires the ability for a peripheral to wake the computer from sleep. Optional for TB3.
  • DMA memory protection: TB4 requires it. Supported, but optional for TB3.
  • USB4 specification: TB4 is compliant. TB3 is compatible, but may not support all of its features.

Personally, I would prefer TB4 over TB3, all other things being equal. But if there’s a significant difference in price between the two for a product, I would opt for the less expensive product, unless I have an actual need for one or more TB4 features.

See also: Intel: Thunderbolt™ 3 vs. Thunderbolt™ 4 Technology: What’s the Difference?.

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Agree with all that @Simon says (except perhaps the $10 for a TB enclosure is a typo? :slightly_smiling_face:)

I would add that macOS sees external Thunderbolt drives as virtually equivalent to internal ones and things like SMART and TRIM are supported automatically, though not essential.

Also important to say that, from the start of Silicon, booting from externals on Silicon Macs has been flaky with both USB and TB. Sometimes it has worked and sometimes it doesn’t. So much so that Mike Bombich of CCC has made bootable clones a legacy best endeavors option. Ref .

I gave up external dual booting in favour of internal dual booting from another volume in the same container, which is the the Apple recommended way and completely reliable.

Yesterday for unrelated test purposes I tried to do an install onto a TB external (Crucial NVMe in Orico) and it failed. I have often successfully booted externals on both USB and TB, but not this time. I did the test successfully on an additional install on the internal.

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