Fusion Drive Problems...Help!

I have a late 2015 iMac with a 2TB fusion drive. I’ve been getting errors from Drive Genius 5 telling me “APPLE SSD SM0128G Media (disk1) appears to be in critical condition. In the recent past this drive has had one or more issues. These issues should be reviewed using the DrivePulse Event Viewer as soon as possible.” I researched replacing the SSD and called my one and only local Apple Authorized Service Center to find out how much it would cost to replace the drive. They were telling me things like the fusion drive is one complete unit, the SSD is only 8GB and I cannot boot off off it (I have 128GB and do boot off of it), my entire mother board would have to be replaced, etc. When I questioned the two guys that I spoke to, they got very defensive and angry. Needless to say, I do not feel comfortable taking my computer to them. I’m too scared to try the installation myself. I was hoping for some suggested options. Should I try reformatting? I’ve read about another option of an external thunderbolt enclosure with an SSD drive…Is this a good option? Should I attempt the installation myself. Should I buy a new computer? Sorry for how long this is. I appreciate any help!

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Those guys got defensive because they were wrong about what they told you about Fusion drives. Your OS runs from the SSD. The spinning HD is for storage. They both work in harmony because of the Fusion setup.

Your iMac has a separate spinning HD and a SSD. Both drives are paired together via software (hence the term Fusion). Drive Genius is telling you there may be an issue with your 128gb SSD. Please run Disk Utility from the Recovery Partition to verify. Command+R at startup will allow you to do this. Please let us know what the results are. You can also have Applecare help you run Diagnostics by giving them a call.


I deleted a previous answer. I thought over this one. I think the guys misundertood something you said and thought you were talking about RAM. Basically that makes sense of the 8GB figure. I also believe that on the 2015 model the RAM is soldered onto the motherboard: that makes sense of what they said regarding that, you also cannot boot off the RAM so that fits too: though it was not what you were really asking about, they either misheard you or habit regarding stuff they get asked about all the time misdirected them.

They thought you wanted to upgrade the RAM. I would try them again. The rest of this reply is just some discursive points that are not important.

I suspect, strongly, that you and the guys got your wires crossed. It is a pity they got sharp with you: try again and schmooze a bit, they might have been frustrated rather than really angry. IT can be very hard to convey over the phone or verbally. Often people I speak with understand ‘memory’ or even ‘Solid state memory’ to mean RAM. That is the only way they would have got the 8GB figure.
It can also easy to be patronizing to people when trying to glean answers on the one hand, and brow beating technical on the other and one gets brickbats on both sides of that balancing act.

Other than that, a lot of hardware may as well be treated as ‘one unit’, even if, in principle or with special gear or skill, you can, for example, change one piece and not the other. At one time once could replace in a modular fashion pretty much everything in a computer: much that is now printed into chips even.

The fusion drive is especially hard to explain verbally. Your Fusion, according to Apple themselves and contrary to what @MacGuyMI says, will use the SSD for storage if the system decides something is used a lot. It is tricky conceptually and not much is gained by fine-graining it in my view.
They give a spreadsheet as an example of something that might well get ‘stored’ on the SSD if you use it a lot. So the system is making a lot of storage decisions on your behalf. Your OSX, is anyway, in some sense being ‘stored’.

Fusion Drive is ‘logically’ one thing; well mostly…, but physically, by definition, two: one spinning one solid state. But pragmatically, from a repair point of view, it might well be ‘an unit’ along with some cable etc. etc. etc… Again I don’t know but suspect it is. I saw some iFixit pages which suggest Fusion can be treated as two component parts, but when I read the procedures… well good luck with that. Again maybe to a skilled technician it looks like an easy job? To me it looked impossible to do without breaking something along with any warranty you might have.

However I am sure you really were talking at crossed purposes with your dealership Try them again, really I would.

Thank you TudorEynon and MacGuyMI. I appreciate your help very much. TudorEynon…I don’t think that they thought I was talking about RAM since we were specifically talking about the SSD drive and the spinning drive components of the fusion drive. I’ve researched this pretty well and know that people replace one or both of these drives…I just wish it was easier to do. So…I booted my computer from another HD and ran Disk Utility - it said everything appeared to be okay on both the SSD and the HDD. Then I ran Drive Genius again and it still warns me of a possible hardware error and could not even complete the check. Should I trust Drive Genius? Should I try reformatting? Other options? Thanks once again.

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Just to say it out loud, I assume you have multiple backups?

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yes exactly!, I am sure the guys at the service place got their wires crossed. I really am. However I would just keep running it if I were dbos and make sure I had several back ups and see what happens.
I would take it into a service center or call Apple direct.

Really @dbos everything indicates they got their wires crossed at some point during the conversation, I have had it happen to me believe me. Apple rides their accredited centers quite hard and they wouldn’t be so ignorant about a Fusion drive?
Phone Apple direct is what I would advise, find a phone number on the Apple site under ‘support’. Have your ID and so on at hand and the full details of your system and numbers etc. Take screenshots of the warning messages and any test results from elsewhere.

It does happen that warnings arise for obscure reasons and can be in themselves ‘faulty’ in some way or triggered by something marginal. Try the call line. I saw on iFixit once pages on how to do what you are thinking about. It looked really tricky and inadvisable in my view and risked breaking everything. Good luck!

I will be away for a week now and won’t have my computer with me. Try IMessaging Rose Orchard or Katie Floyd here if you get no luck with Apple Support. I think Apple will certainly advise you not to open the machine and to take it to the service center. Let me know out of interest would you here what happens?

Yes…lots of backups! In fact, I’m making another as we speak. Thank you very much for your help. I will reach out to Apple.

My description of how the Fusion drive setup was meant to be basic and overly simple.

Yes, a Fusion partition/setup keeps the OS on the SSD and other files on the HD. Yes, frequently used files will reside on the SSD to provide faster access. I believe Apple also originally stated that programs would run from the SSD in the same manner.

I agree with TudorEynon that the AASP you spoke with are confused about what you requested of them. But that doesn’t excuse their behavior for treating you the way they did.

Typically when it comes to Fusion drives… the spinning HD fails long before the SSD will. SSD drives are more like a light switch. They are either on or off. Rarely an SSD will fail slowly like a traditional HD. But I make that statement based on having only thirteen years experience as an Apple Certified Technician. Some AASP firms have surprised me in the past over what they don’t know. Some have provided great knowledge.

If you reside in the US, you can call 1-800-APL-CARE for support. Ask them to run MRI and Storage Diagnostics on your iMac. I wonder if Drive Genius may be providing false errors because of the Fusion software.


Fair point about those guys @MacGuyMI . I agree with you: one has to learn patience. I also agree that your simplified description was more useful and helpful than mine. Sorry to add an unecessary complication which is what I did probably. This site is really useful for exactly the reason that we stay out of the weeds. Fusion is actually very complicated in my view… at some level. Thanks for your nice rejoinder I appreciated it.
I agree also that Apple would be the best place to help. I will add, out of interest that my own experience doesn’t extend really to any practical use of fusion drives and I am lucky enough to have low needs and can easily manage everything I do with smallish SSD. I made a deliberate decision to not use spin drives any more a few years ago. I still have some hard drives for backup on spin. One broke after a few months, a Seagate…