Is my 2017 iMac just getting old?

I have a 2017 iMac with a 2 TB Fusion Drive (1.53 TB available) and 16 GB of RAM running the latest version of Monterey. A couple of weeks ago I started noticing a lack of responsiveness, sometimes accompanied by a spinning beachball, several times a day. Since then it has got progressively worse and now happens several times an hour, and it happens randomly in any application (Alfred in particular has become almost unusable). According to the Activity Monitor, Memory Used is about 8–9 GB and Swap Memory remains constant at 3.8 MB. When the computer becomes unresponsive, the Activity Monitor shows that the application in question is not responding, but there does not seem to be any jump in memory usage. I am not doing anything that requires lots of resources, such as video editing.
What do these symptoms tell you? Is there anything I can do to treat them, or is the computer just getting old?

As soon as I saw “Fusion Drive” I thought: back everything up if you haven’t, and run a disk utility to check your drive, pronto.

That said, I would have thought the same things just from your description, without knowing it was a Fusion Drive.


Check your drive with Disk Utility, using Safe mode.

Backup everything you’ve got onto an external drive and do a thorough drive check! Sounds like the fusion drive is about to die on you


If you haven’t followed the advice above already, PLEASE backup all data right away. Hopefully you have a backup plan in action currently.

Then boot into Safe mode and see if the same issues persist. I am not a fan of Fusion Drives as they tend to fail between 5-7 years of age. If everything runs smoothly in Safe mode, you probably need to reinstall your OS. If not, prepare to replace the HD soon. I would recommend swapping the spinning HD for a SSD.

I agree — the few Fusion Drives I’ve seen have had failures that start off with annoying but not life-ending problems that slowly escalate. Usually the cost of replacing the drive sends my clients to buying new computers (they’re not DIY-ers).

If it is a FusionDrive it is often, as with my system, a failure of the build in SSD.
I have bought an external T3-SSD case, and placed a SSD inside to run my system from this one, and it works pretty well. If I remember correctly I wrote somewhere else within MPU about it, but could not find it at the moment.
You can also, thereafter, divide the FusionDrive into its SSD and HDD parts, and use the HDD further on, if the degradation did not also affect the HDD, which could be evaluated with an App like DriveDX to check (and monitor) the status of your drives.

Thanks for all the helpful advice. I booted in Safe mode and ran First Aid in Disk Utility, which found no problems. Is this a reliable indicator that the Fusion Drive is not failing? I will continue using Safe mode for a while to see whether the issues recur—so far they haven’t.

No, unfortunately not.
DiskUtility seems not to be able to detect a failing SSD.
I would recommend to run the App (Testversion will be sufficient) I linked above to get information about the SSD part of the Fusion Drive.
If it is failing, you have the diagnosis, if it is (still) OK, you have to have a look for an other possible reason for your problems.
But acc. to your description above, it seems to be very similar to what happened to my 2017 iMac a couple of month ago.
And regarding the SSD, it is still not a question if the SSD will fail at some point, but still only when this will be!

I installed and ran DriveDx, and it found that the SSD part of the Fusion Drive is in good health but the HDD is failing. What do you recommend that I do (apart from backing up of course)?

You could:

According to the link you provided, my iMac is not compatible with an external SSD startup disk. I guess I’ll start looking into the other two options.

I just saw some articles on the web about splitting the fusion drive into separate SSD and HDD components. Don’t know if this means that you could put MacOS on the internal SSD and not use the internal HDD. This would also depend on the size of the SSD portion of the fusion drive. I am not knowledgeable enough about this so I don’t want to share a link but you could search for yourself. Maybe someone here knows more about this. Good luck.

You have a 2017 27’’ 5K, right?
That would be the same system like my one.
The linked article is misleading on that, as it seems that the approach of this article just was, to replace an internal HDD by an external SSD for SpeedGain, and therefore just not looked at the iMacs with a FusionDrive who already have the SSD Build in, so there is no Speed Gain available, with that replacement.
In your Situation it is something different. While it is unusual, that the SSD-Part of the FusionDrive is still fine, and the HDD failed, it is for sure not impossible.

  • You could now separate the two drives with DiskUtility, use the internal SSD for the OS, and place your Data onto an external HDD.
  • You could replace the internal FusionDrive, by yourself, or with a ServicePartner of Apple. Both has the risk to damage the Display, with ending up in replacing the rather expensive display panel, too.
  • You could buy a new iMac.
  • Or you could replace the internal Drive by an external Thunderbolt3-SSD.
    I did the last one with this SSD
    and this casing

and I have a Superfast System back.
There are a lot of descriptions how to do the replacement out there, and the one I used are in German, so you have to have a look for yourself, but it is pretty much just put the SSD into the Case, plug it in, and do what the System required to use it as the new Startup Drive. Then you could use TimeMachine, CCC or whatever your Backup system is, to play the Backup back, and you are ready to go.
Some sidenotes:

  • The Case came with some kind of a “rubber panel”, a lot of people in the installation videos are throwing away. This panel is made of a kind of a gel, that transports the heat. You have to peal the coversheet of, on both sides, and place it directly on top of the SSD after the installation, and make sure, that the Metalplate inside the Top of the case, that you screw back onto the case, gets in contact to this gel, to get a good heat spread towards the case.
  • I placed the case flat onto the Metalfoot of my iMac, which improves the Heatdevelopment significantly, as I could use the Foot as an additional “Heatspreader”.
  • I always use a situation like that, to rebuild my system in total, so to get the OS new from the Internet, and all Apps from the App Store, and just play my pure Data back from the Backup. With this you could make sure, that also all of those little Software kinks building up partly over years in an old system are eliminated, and you are good to go for the next couple of years.

There are plenty of descriptions to do all of this, also from the Apple Support Side, I would in general recommend to read/view to be sure what you did when you do it this way!

P.S.: It seems that you could use the description, of how to do it, of the linked article also for the replacement like I described it. Seems to cover pretty much everything that is needed to get the external SSD running. Just make sure, you get a real T3-Case, not an USB 3.x case!

1 Like

When I had a regular hard disk failing on my Mac Mini the symptoms were the same. It was very obvious because in there were a lot of error messages related to the drive. I could not detect any data loss because I think either the OS or the disk firmware was busy reallocating damaged sectors, but the computer would slow to a crawl.

Thanks for the detailed explanation. Lots to think about. But I may have to act quickly, because things are starting to slow down in Safe mode too.

One further question. What is the difference between using the internal SSD for the OS and an external HDD for data and replacing the internal drive with an external SSD? Is one preferable to the other?

The HDD started to fail on my 2017 27” iMac. I am booting from an external 2 TB Samsung T5 via USB-C/Thunderbolt. I used Carbon Copy Cloner to set up the external drive.

Fusion drives were offered as a way to get large capacity storage at a lower price point when SSDs were more expensive. The OS went on the smaller SSD for speed, and data storage went on the HDD. SSDs are cheap now, so there is no point using an HDD, let alone recreating a fusion drive by using the internal blade SSD from the fusion drive (it is at best 128 GB) and a new HDD.

Really, you have two options if you want to keep using your iMac:

  1. Crack open the iMac and replace the HDD with an SSD. By your questions, I suspect you won’t be DIYing this, so you have to decide if the cost of paying someone to do this for you is worth it for a 5 year old computer.
  2. Purchase an external SSD - I suggest the Samsung T5 or T7, either will work. Clone your internal drive to the SSD (e.g., with Carbon Copy Cloner). Tape the SSD to the back of your iMac and plug it into the Thunderbold port. Turn on your computer and it will run as if the drive were internal. This is the cheaper option of the two.
1 Like

I would say, it is all about the speed.
The Fusion Drive is, as far as I understand, using the SSD part, to store the data used frequently, to expedite the reaction of the iMac. This is (parts?) of the OS, and some Data and Apps often used.
Everything else remains stored at the HDD, and took a little bit longer, to get loaded, if needed.
While you can see two different drives, if you have a look onto the FusionDrive with DiskUtility, the often named by the OS as “HD Data”, and “HD” specified partitions did not equal with the physical SSD and HDD.
If you now divert the FusionDrive into the physical SSD and HDD, you can of course use the internal SSD for the OS, and an external HDD for the Data.
However, there would be a significant decrease in the Speed, as all Data and Apps, also the frequently used, are now on the significant slower HDD.
This could be circumnavigated, of you use an external SSD with a fast connection like Thunderbolt3.
And if you have everything on this anyway, you could also place the OS onto it, while it is still possible, to stay with the OS on the internal SSD.
I think the last approach (internal & external SSD) is just not common, because in normal cases, the internal SSD will die timely before the HDD, so the common use case is just to put everything on the external one.
My system is running fine with the external setup, and I am very hopeful, that my 2017 iMac will be with me, at least until Apple will not longer support the OS on this system.