Replacing Ventura Fusion drive with SSD fails

(with Startup Security Utility set to “reduced”).

Why? You don't need to reduce security to boot from an external drive. Just enable booting from an external drive.

(External drive not available as startup, BTW.)

A clone's not a clone anymore.

The iMac refuses to recognize the new 2TB SSD, internal or external. Produces blinking question mark.

That would indicate it's not really a valid startup drive.

Installed drive to the iMac anyway. Reset PRAM, no change, using wired keyboard/mouse.

Running online recovery from iMac: Disk Utility produces Code 8 errors all around.

Connected target disk mode to Mac Mini, drive mounts and verifies correctly as before.

Taking iMac back to online recovery, the reinstall OS option produces installer for OS Sierra, 10.12.

You may have to install Sierra, then upgrade. Once upgraded, Migrate from your Time Machine backup.

I have little faith in TimeMachine backup, but there is a one - if I can find it - will try that next.

Is there a reason you can't make a backup, now? Did you start all of this without a current backup? Maybe get another drive and use the clone you made to migrate from. No idea if that will work, though. I guess if you pulled the two drives, they may not be fused anymore.

Meanwhile, if anybody has some magic to obtain Apple’s blessing for this relatively simple upgrade, any/all suggestions would be gratefully received. Thanks.

It is simple. You tried to make it difficult by cloning Ventura. That's not simple anymore.

With a valid Time Machine backup, install a bare SSD, Install whatever OS it offers, upgrade, Migrate. If you can't install Ventura straight away, create a user that does not share the same name as the ones you wish to migrate later.

Instead of installing Sierra and upgrading, create a bootable installer for Ventura on that Mac

You can’t clone any recent version of macOS. You would need to erase the external drive, download the OS installer, and select the external as the target for installation. Then you could copy your data using Migration Assistant or similar.

However, you may not notice very much improvement. An external SSD is going to be limited by your (probably USB) bus. Thunderbolt would be much better, but those are hard to find.

If the mechanical part of your Fusion Drive is failing or just spectacularly slow, as some of them are, then the above may not apply. In those cases, even a clunky USB SSD can be better. But if this is the case, I recommend that you erase both the internal SSD and HDD portions and don’t use them. Even having any data on the HDD could slow down the system.

I have done what Barney suggests and can attest that it does work.

"... install a bare SSD, Install whatever OS it offers, upgrade, Migrate. If you can't install Ventura straight away, create a user that does not share the same name as the ones you wish to migrate later."

I offer up our late 2015 iMac, originally shipped with 10.11, El Capitan, had been running High Sierra but with a slow HDD. El Capitan (10.11) is what is installed by Internet Recovery on a new bare SSD, which we installed to replace the original HDD. I then upgraded to 10.12 Sierra, then 10.13 High Sierra, then 10.15 Catalina (skipped Mojave), then Monterey 12.6.7 (skipped Big Sur). This is the highest MacOS for this iMac. It sounds laborious but once you start plowing through these MacOS versions, it goes fast, and very smoothly, especially with a good internet connection and an SSD inside. Maybe a few hours. Since the machine is basically factory bare, there are no complications, and as we did this we had a single administrator user called ADMIN. After reaching the final MacOS 12.6.7 (Monterey), I then ran Migration Assistant on the Time Machine backup previously made from a much older MacOS migrating over ONLY accounts and files but no settings and no software.

This is basically what Barney suggests (except your iMac is newer and can go to Ventura, mine stopped at Monterey).

This is a very smooth and trouble free way to quickly get to the final MacOS from a bare, new internal SSD. No fuss with an external drive Ventura installer (which should work also but this other method just requires one session with internet recovery, followed by simply selecting Software Update and clicking "install" several times).

Motorcycle Michael wrote:

Time Machine has lost its key feature, namely the ability to copy or restore a bootable volume.

This was never a feature of Time Machine. I have seen innumerable fights over Time Machine vs. cloning tools over the years. I can assure you that Time Machine never, ever did that.

At one point, Time Machine did include its own Recovery volume, thereby making it "bootable". But again, I can assure you that no proponents of cloning tools ever accepted this capability as 1) actually being bootable, 2) actually existing at all, or 3) ever having been typed in the online dispute. On the rare occasions that they did acknowledge the fact, it was irreverent because it wasn't absolutely instantaneous like a cloning tool, thus making it unsuitable for restoring a Mac from backup, which had to be done at least 4 times each week.

I honestly don't know if the current version of Time Machine still includes a recovery volume. It turned out that in 20 years of those pointless fights, I've never once needed to boot from the Time Machine recovery volume. Given the secure boot requirement of recent Macs, it seems logical that this is now a moot point. It makes sense to have removed this feature.

there was no problem with the Fusion drive other than being intolerably slow due to a tiny SSD + APFS HDD.

If your Fusion Drive was intolerably slow, then there was most definitely a problem with it. But you didn't ask about that. You asked about cloning. As far as I can tell, you haven't even tried setting up the external as a boot device.

We put Monterey on the new 2TB SSD after reformat, then discovered that migration from 1TB Ventura clone into Monterey worked flawlessly - all without 6-8hour downloads thru online Recovery (which only allowed Sierra). Thru all this, the Time Machine backup proved to be useless (since reformatted to Monterey).

You can't restore to a previous operating system. You can erase the hard drive and restore the old version. But any apps, especially Apple apps, are going to be totally confused. If it works at all you will be plagued by odd problems forever.

Misinformation? I must be onto something ;-)

Time Machine has lost its key feature, namely the ability to copy or restore a bootable volume.

Making a bootable backup was never a feature, much less a "key" feature. Backing up the OS was a feature of Time Machine when it was possible, but it certainly wasn't a "key" feature. Backing up your data was the only "key" feature of Time Machine.

If I may, Carbon Copy Cloner has made tremendous strides in creating a "Bootable System" to be pretty reliable in doing so. I have 3 drives all 1TB, a Samsung 860 EVO SSD internal, and 2 Western Digital 1TB NVME's connected via Thunderbolt, all of which are bootable. I've tried all 3 with success, numerous times in testing the viability of "Bootable" backups or Migrating on a new OS successfully, yes AppleID is asking for passwords, Carbon Copy Cloner is warning that you're booting off a "Backup" and having you "review" all your scripts (Tasks) and the "normal" routine when installing a new OS, a "Bootable" backup or Migrating. So ultimately it works at least for me at or near 100% of the time.

I've been using CCC since High Sierra on a 2011, 2015 iMac and now a 2019 iMac, and rarely (I can't recall a time, but people freak out at 100% ) has it failed in creating a bootable volume, whatever OS.

I run my iMac off of an external NVME, substantially faster than the internal SSD.

2019 iMac 19, Ventura 13.4.1

3.7 GHz

64 GB of RAM

Sys Firmware 1968.120.12.0.0

I hope this helps with a "Bootable" Volume.

Startup security isn’t the problem. As I already stated, if Sierra is all the is available, install that, then upgrade. When you’ve gotten to the same OS you have in a backup, Migrate from that.

Time Machine backups have never been bootable. Now, there isn’t even an OS backed up on them.

Recovery is still there. It sure where you are getting all of the misinformation.

The point of TM is still the same, to safeguard your data.