27" iMac Retina 5K Late 2014 Fusion Drive problem

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Level 1

9 points

27" iMac Retina 5K Late 2014 Fusion Drive problem

Hi my 27" iMac Retina 5K Late 2014, 3TB fusion drive appears to have a Fusion Drive problem. It won't boot up. When I power up I get the Apple "Bong", the Apple splash screen and the progress bar appears but the progress bar stalls about one third of the way through and the iMac hangs.

I have tried starting up in Safe Mode and in Recovery Mode and sometimes I can run Disk Utility which shows the drives. When I run Disk First Aid no issues appear to be found with either the SSD or the HDD. Sometimes I can start up in Safe or Recovery mode but most times I get the Startup Progress bar and the iMac hangs.

I have reinstalled MacOS Big Sur via Internet Recovery but the problem still remains.

Am I right in thinking that the SSD part of the Fusion Drive stores the MacOS and that it is the SSD that is more likely to have failed? Or would my issue likely to be with the HDD or perhaps both SSD and HDD?

Thanks in anticipation,

Tom

iMac 27″, macOS 11.7

Posted on Nov 20, 2024 6:14 AM

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Answer 1

den.thed

Level 10

82,564 points

Nov 20, 2024 7:11 AM in response to Tom Murphy1

Generally the usual causality is the HDD.

Given the iMac's age, only a limited number of AASP's will service and replace the faulty drive.

Find Locations

With that in mind, consider replacing that iMac with a new Mac and migrate from your Time Machine backup.

Mac - Which Mac is best for me? - Apple

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Answer 2

den.thed

Level 10

82,564 points

Nov 20, 2024 7:48 AM in response to Tom Murphy1

Paying someone to fix the iMac is totally up to you.

Just keep in mind, that it could die at anytime for other reasons.

Personally I would replace the iMac with an aftermarket 27" external display for a couple of reasons.

1) An external display will use far less energy than running the iMac.

2) An external display will be far more reliable in the long run.

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Answer 3

den.thed

Level 10

82,564 points

Nov 21, 2024 4:28 PM in response to Tom Murphy1

1) The details in the Disk Utility screenshot are hard to see in Dark mode.

2) Go to the small View box in Disk Utility, select Show All Devices and take a few more screenshots with the different volumes highlighted.

Tom Murphy1 wrote:

I'm thinking of erasing the built in HDD in the iMac and reinstalling Big Sur on that to see if it would work. Is there anything I should be aware of re erasing the drive as it is a Fusion Drive? I've attached two screen shots- 1 Disk Utility 2. Get Info. As you can see something is not quite right!

You can most certainly try that, see > Use Disk Utility to erase an Intel-based Mac - Apple Support

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Answer 4

Allan Jones

Level 9

72,380 points

Nov 23, 2024 9:59 AM in response to Tom Murphy1

Rather that use Disk Utility, try the simple test outlined near the top of this Apple article:

How to fix a split Fusion Drive - Apple Support

At least we can eliminate a common cause of Fusion problems that way.

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Answer 5

Tom Murphy1 Author

Level 1

9 points

Nov 21, 2024 1:59 PM in response to D.I. Johnson

Thanks for the suggestion. I've attached an external drive and am now booting from that. It's slow but at least my iMac is working. I'll see if it is fast enough to do what I want.

I'm thinking of erasing the built in HDD in the iMac and reinstalling Big Sur on that to see if it would work. Is there anything I should be aware of re erasing the drive as it is a Fusion Drive? I've attached two screen shots- 1 Disk Utility 2. Get Info. As you can see something is not quite right!

I've run Drive DX and it appears I have a failing HDD. I'm presuming that erasing the HDD is not going to solve my problem. How do I add in the DRiveDX report to this comment?

Any help appreciated.

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Answer 6

Nov 20, 2024 7:40 AM in response to Tom Murphy1

Since the iMac is only a monitor at this point, I wouldn't bother replacing the hdd. It would be much easier to get an external drive and install macOS to that, then use it as the startup drive. When you're done with the iMac as monitor, reuse the drive with whatever Mac you are using at the time.

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Answer 7

Tom Murphy1 Author

Level 1

9 points

Nov 23, 2024 8:31 AM in response to D.I. Johnson

Thanks for the suggestion. I've attached an external drive and can now use the iMac as an additional screen. I'll give it a few days to see how I get along with it but so far it seems to be working ok, slow boot but that's fine.

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Answer 8

Tom Murphy1 Author

Level 1

9 points

Nov 20, 2024 7:20 AM in response to den.thed

Thanks for that info. I use the iMac as a second screen attached to a Mac Studio using Luna Display so replacing the HDD might be the way to go. Thanks.

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Answer 9

Tom Murphy1 Author

Level 1

9 points

Nov 23, 2024 8:32 AM in response to Tom Murphy1

Hi,

I think that the HDD is failing so I'm going to boot from an external drive and see how that works. I might end up installing a new HDD into the iMac and again thanks for your help.

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