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Clone problems

1974darrenh

1974darrenh

macrumors member
Original poster
Apr 27, 2024
33
13
I'm normally a “Windows" man but someone has given me an iMAC Retina 5K 27 inch 2017, running Ventura 13.7.8

Im trying to upgrade it to an SSD but all the clone processes fail.

Firstly I used “Disk Utility" which fails and shows a “OSStatus error 49157.

I then tried “Carbon Copy" which I thought was working, but when I tested the new SSD, it wasn't showing in the startup disks so I couldn't select it to boot from.

Has anyone got some advice or recommendations of other software I could try? As I said, I'm a newbie when it comes to MacOS stuff.

Thanks in advance.
 
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Does the iMac boot to Ventura now?
Can you get logged in to an account and be in the finder?

Tell us about the SSD.
Is this an external SSD?
If so, does it connect via USB or thunderbolt?
Or... is it an internally-installed SSD?

Tip for erasing the SSD:
If it won't erase to Mac format, then...
...Try erasing to a "PC format" first.
Try exFAT. Does that erase it?

Once you've done that, do THIS:
Now erase it "back to" a Mac format.
Use APFS, GUID partition format, and BE SURE that it's "case INsensitive".
DON'T use "case sensitive".

Does that work?

If so, then try CCC.

BETTER SUGGESTION:
Since you're a PC person (perhaps not well-versed in Mac?), I'll offer another app to try:
SuperDuper.
SD is FREE to use for the job you need.
It's also one of the easiest-to-understand and use apps out there.

You can get it here:

Let us know how you make out.
 
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It boots to Ventura and I can log in (only on the installed hd, not the new SSD)

The SSD is external. My intention is to clone the old drive to the new SSD then install that in the iMac as the main bootable drive.



Thanks. I'll try your tips and get back to you.
 
Failed too 😞
IMG_20251128_170947.jpg
 
What does the SSD setup look like in Disk Utility….?
Can you manually drag and drop files to the SSD from Finder?
 
I've tried reinstalling Ventura over the top of the original and it came back with no errors.

I also tried “First Aid" on all the drives too and it came back with no errors.
 
Clone only in recovery mode.
Some USB chipsets in external enclosures don’t play nice with latest macOS releases.
 
OP:

How much prior experience with a Mac do you have?

For now...
Disconnect the external drive.
Open disk utility.
VERY IMPORTANT -- go the "view" menu and choose "show all devices".
Take a screenshot of the disk utiilty window and post it here.

If you're "cloning", you shouldn't be seeing anything like "restore"...
 
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1974darrenh said:
I'm normally a “Windows" man but someone has given me an iMAC Retina 5K 27 inch 2017, running Ventura 13.7.8

Im trying to upgrade it to an SSD but all the clone processes fail.

Firstly I used “Disk Utility" which fails and shows a “OSStatus error 49157.

I then tried “Carbon Copy" which I thought was working, but when I tested the new SSD, it wasn't showing in the startup disks so I couldn't select it to boot from.

Has anyone got some advice or recommendations of other software I could try? As I said, I'm a newbie when it comes to MacOS stuff.

Thanks in advance.
Click to expand...
Impossible to clone a Fusion Drive (HDD+SSD, a logical volume) to a single SSD (a physical volume). Use Time Machine/Migration Assistant instead.
 
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Fishrrman said:
OP:

How much prior experience with a Mac do you have?

For now...
Disconnect the external drive.
Open disk utility.
VERY IMPORTANT -- go the "view" menu and choose "show all devices".
Take a screenshot of the disk utiilty window and post it here.

If you're "cloning", you shouldn't be seeing anything like "restore"...
Click to expand...
IMG_20251128_205713.jpg
 
Download the installer to your working Ventura on the HD+SSD Fusion Drive.

Then Start the Installer and choose the external SSD to install on.

When the new fresh System Boots you will be asked if you want to migrate Data from a Backup or HD.

Then Choose the internal Fusion Drive and it will import your System and it is like a Clone.

@AlixSPQR and @!!! told you so already :cool:

Transfer to a new Mac with Migration Assistant - Apple Support

Use Migration Assistant to copy some or all of your content from one Mac to another Mac.
support.apple.com support.apple.com
 
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You said in your OP that someone gave you this iMac.
Is there anything on the drive that you need to save? (exists nowhere else, no backup, really important personal info or pictures, etc)
If not, just swap out the present internal hard drive with your new SSD.
Install Ventura on the new SSD.

Yes, you have a Fusion drive, which is actually two devices: a spinning hard drive, and an NVME card. They are joined together through software, but some files are on one device, some others are on the other device.
Your Fusion drive includes a 2TB hard drive, and an NVME card with 128GB. That's why you have the unusual 2.12 TB capacity.
You might consider removing that 128GB card, too. Not really too useful as an internal, with only 128GB of space, AND it may be where that backup error comes from. (It just makes the SSD more challenging to swap if you decide to remove the old SSD card, too. It's on the back of the logic board, which has to be completely removed to get at the old SSD slot.

I wonder if someone gave you this iMac, because they were already having intermittent problems.

It's probably not a coincidence that the system volume copied OK with 118.44GB, almost same as the SSD card capacity (128GB), but the data volume (which is, well, data added; personal files/pictures/documents/etc. That errors out.
So, something going on with the fusion drive. I suspect that one of the devices is failing.
 
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genexx said:
Download the installer to your working Ventura on the HD+SSD Fusion Drive.

Then Start the Installer and choose the external SSD to install on.

When the new fresh System Boots you will be asked if you want to migrate Data from a Backup or HD.

Then Choose the internal Fusion Drive and it will import your System and it is like a Clone.

@AlixSPQR and @!!! told you so already :cool:

Transfer to a new Mac with Migration Assistant - Apple Support

Use Migration Assistant to copy some or all of your content from one Mac to another Mac.
support.apple.com support.apple.com
Click to expand...
Ok I've followed the instructions and all is going well so far. I have just started the migration process from the old drive to the new one. Hopefully it will all work out. I'll let you know.
 
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When I wanted to install an SSD into my 2011 21.5 iMac I used Carbon Copy Cloner to copy my hard drive to the externally connected Samsung Evo SSD. I then tested it as the startup disc and it worked perfectly. Next I swapped in the SSD and ran it that way for six years without any issue.
 
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Bootable Clones from Big Sur to Sequoia and Tahoe: What Works, What Breaks, and Why Migration Assistant Remains the Reliable Path



Overview



Up to the HFS+ era (for example on 2011-generation Macs), Carbon Copy Cloner (CCC) could create a fully bootable external clone with a normal copy of the startup disk. Starting with macOS Big Sur (11) and continuing through Ventura (13), Sonoma (14), Sequoia (15) and Tahoe (26), Apple’s startup-disk architecture and security model changed in ways that make bootable cloning:

  • non-traditional (requires Apple’s own replication tool),​
  • fragile across macOS updates, and​
  • especially inconsistent on Apple-silicon Macs unless the destination is presented over a Thunderbolt connection/path.​


Installing macOS on the target disk and restoring via Migration Assistant from a CCC Standard Backup is therefore often the most dependable “clone-equivalent.”

1. Core Platform Change Since Big Sur (11) — Still True in Sequoia and Tahoe

1.1 Signed System Volume (SSV)

From Big Sur onward, the startup disk is an APFS Volume Group:​
  • System Volume (SSV) — read-only, cryptographically sealed​
  • Data Volume — read/write (apps, home folders, settings)​

Only Apple can create or re-seal the Signed System Volume. A plain third-party file copy no longer produces a bootable macOS system.

1.2 Apple ASR/APFS Replicator Is Required

Bootable clones are only possible when the System volume is copied using Apple Software Restore (ASR) / APFS Replicator. CCC can invoke this Apple tool through its Legacy Bootable Backup Assistant; CCC’s normal file-copier cannot seal macOS itself.

1.3 Bootable Clones Are “Ad-Hoc”

Modern macOS security makes external booting too fragile to be a primary long-term backup/recovery strategy. Bootable clones are now best treated as ad-hoc tools for migration, testing, or short-term fallback.​
2. What CCC Can Do on Modern macOS (Big Sur → Tahoe)

2.1 Standard Backup (Recommended Default)

CCC Standard Backups reliably preserve:​
  • applications​
  • user data​
  • settings​
  • all Data-volume contents​

They are fully restorable and ideal for Migration Assistant, but not bootable on Big Sur+ by themselves.

2.2 Legacy Bootable Backup Assistant (Bootable, With Limits)

CCC can still create a bootable system on Big Sur and later only via the Legacy Bootable Backup Assistant, which runs ASR to replicate the sealed System volume and create the paired Data volume.

Key limitations that remain through Sequoia and Tahoe:​
  • The sealed System volume cannot be updated incrementally by third-party tools. After macOS system updates, keeping a clone current typically requires erasing and re-creating the bootable clone.​
  • Bootability depends on Apple firmware + ASR behavior; results vary by OS build and hardware path.​
3. Intel Macs: Why a Big Sur/Ventura/Sonoma/Sequoia/Tahoe Bootable Clone Can Fail (Example: iMac 2017)

Even on Intel Macs without a T2 chip, bootable clones may fail for practical reasons:

3.1 Legacy Assistant Not Used

Standard CCC tasks copy only the Data volume. Without ASR replication of the sealed System volume, the result is not bootable. This is still the most common misunderstanding in forum threads.

3.2 Target Disk Not Properly Erased / Prepared for ASR

ASR expects a clean APFS destination volume group. If the disk is not erased or contains incompatible roles/partitions, ASR replication can complete but still yield a non-bootable group.

3.3 External Enclosure / USB Bridge Problems

Bootability can fail due to enclosure firmware, USB bridges, cables, or port stability even when the clone itself is correct.

3.4 Clone Staleness After macOS Updates

After any macOS update, the source System volume changes. A previously bootable clone can become stale and refuse to boot unless re-created or macOS is installed on the target again.​
4. Apple-Silicon Macs: Why a Thunderbolt Connection/Path Has Been the Reliable Route

4.1 Practical Reality Since Ventura (and often beyond)

On Apple-silicon Macs, Apple’s ASR replicator has been inconsistent when the destination is connected directly over USB. Presenting the destination over a Thunderbolt connection/path has yielded far better reliability.

4.2 This Is About the Thunderbolt Bus, Not “Thunderbolt Storage”

A Thunderbolt-native SSD enclosure is not strictly required. What matters is that macOS sees the destination as Thunderbolt-attached.
Examples that often work:​
  • a USB SSD connected through a Thunderbolt dock/adapter​
  • a storage device whose upstream path to the Mac is Thunderbolt​

Direct-USB destinations may still boot on some chipsets, but results are not consistent enough to rely on.

4.3 If Only Direct USB Is Available

The stable workaround remains:​
  • make a CCC Standard Backup to USB, then​
  • install macOS on that USB volume, and​
  • migrate data with Migration Assistant.​

This avoids depending on ASR-to-USB bootability.

4.4 External Boot Is Not a Full “Rescue Disk” on Apple Silicon

Apple-silicon Macs still require functional internal storage to boot at all. External booting cannot revive a machine with a dead internal SSD.​
5. Sequoia (15): The 15.2 Regression and the 15.3 Fix​
  • macOS Sequoia 15.2 introduced a bug in Apple’s replication/ASR path that prevented CCC and SuperDuper from creating new bootable legacy clones.​
  • macOS Sequoia 15.3 fixed that regression, so bootable clones can again be created using CCC’s Legacy Bootable Backup Assistant.​

This does not remove the Signed System Volume rules; it only restores the Apple tool chain that third-party bootable workflows depend on.​
6. Why the 2011 CCC Success Story Was Valid — and Why It Doesn’t Map Forward

A typical pre-SSV story is:

“In 2011 CCC cloned the internal HDD to an external SSD, the SSD booted, then it was installed internally and ran for six years.”

That workflow was fully valid under the 2011-era macOS design:

Back then (HFS+, no APFS/SSV):​
  • macOS lived on a single writable system volume.​
  • No cryptographic sealing existed.​
  • CCC produced immediately bootable clones via normal copying.​
  • Incremental updates kept clones bootable long-term.​

From Big Sur onward (through Sequoia and Tahoe):​
  • System and Data are split into an APFS volume group.​
  • The System volume is sealed (SSV).​
  • Ordinary third-party copies cannot become bootable.​
  • Bootable clones require ASR and often need re-creation after OS updates.​

So the 2011 experience is accurate for that era; it reflects a different architecture from current macOS releases.​
7. Tahoe (26): What Changes and What Doesn’t

macOS Tahoe continues Apple’s SSV + APFS volume-group model, so the same cloning constraints apply:​
  • bootable clones still depend on ASR,​
  • maintainability across updates remains fragile,​
  • Migration Assistant restores remain the stable path.​

Tahoe supports external boot and bootable installers, but that is not the same as restoring old-style third-party bootable clones.​
Practical Guidance Summary (Big Sur → Tahoe)

Most reliable “clone-equivalent” across Intel + Apple Silicon:​
  • CCC Standard Backup → install macOS on the target → Migration Assistant restore.​

If a bootable clone is required:​
  • Use CCC Legacy Bootable Backup Assistant on a clean APFS disk.​
  • Expect full re-clones after major macOS updates.​
  • On Apple-silicon Macs, reliability is highest when the destination is presented over a Thunderbolt connection/path; direct-USB targets remain chipset-dependent and inconsistent.​
Conclusion

From Big Sur through Sequoia and Tahoe, bootable clones are no longer a universally stable feature. Intel Macs may still boot from ASR-based legacy copies, but failures are common when the legacy workflow is not applied exactly or when external hardware introduces quirks. Apple-silicon Macs add a further practical constraint: reliable bootable legacy clones typically require that the destination be attached over a Thunderbolt path, even if the storage itself is USB behind that path. Given these realities, installing macOS on the target disk and restoring via Migration Assistant remains the most robust way to recreate a bootable system with current data.
​
 
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