iMac suddenly unusably slow

[jbmillard]

I have an iMac:

Retina 5K, 27-inch, 2019
3.6 GHz 8 core Intel Core I9
64 GB 2667 MHz DDR4
Radeon Pro 580X 8GB
3 TB Fusion Drive

Was initially running Ventura 13.2.

I bought this computer new and have used it for software development without issue for the last three years. I need to run Windows applications so I use VMWare with Windows 8/10 as required.

This Monday morning when I logged in, it was unusably slow. By slow, I mean 30 minutes to boot, 20 minutes to login, 10 minutes to open a window (if the WindowServer didn't crash). It is suddenly completely unusable. For instance, when I click on an option/checkbox, it took 34 seconds to respond.

Things I've tried (with Apple Tech Support help)

1) [Monday] Went into recovery mode (took about 20 minutes), checked HD with DiskUtility - no issues
2) [Monday] Wiped hard drive, reinstalled base OS. Reinstalled back to Ventura 13.2 - still had problem with a default user account
3) [Tuesday] Wiped hard drive, reinstalled base OS (Catalina), then upgraded to Monterey 12.6.2, restored my account and applications, still have problem.
4) [Wednesday] Booted into recovery mode, reinstalled Monterey 12.6.2, logged into my existing account, created a temporary user. Logged out and logged in as temporary user and I have the same problem (in the time I've taken to type this post, it still hasn't opened Safari).

Other things I've noticed:

A) The System Preferences app will not load some preferences. For instance with I click on Sound, I get a long delay and then a dialog that says "Preferences Error - Could not load sound preferences pane". I saw this in both my account and the new temporary account. Additionally, it takes 4 or 5 minutes to get the error.
B) Going into System Preferences, it continually wants my Apple ID. I'm not sure I ever successfully entered it or not.
C) System is very slow to respond to the keyboard.
D) I have been able to bring up Activity Monitor and it doesn't show any particular application with excessive CPU usage. I saw > 97% idle on CPU, ~8 GB of RAM used and hard drive has about 500 GB used.
E) Mouse response appears to be unaffected.

Any ideas?

Thanks!

 

[Juicy Box]

I bet the HDD is starting to fail. Have you tried Apple HW Diagnostic Test? It gives a lot of false negatives, but if it shows a problem, that is usually accurate.

Try de-fusing the Fusion Drive, and install just the OS on the SSD. Try it out and see how it runs. Or, you can do this with an external SSD if you have one available to use.

 

[jbmillard]

I bet the HDD is starting to fail. Have you tried Apple HW Diagnostic Test? It gives a lot of false negatives, but if it shows a problem, that is usually accurate.

Try de-fusing the Fusion Drive, and install just the OS on the SSD. Try it out and see how it runs. Or, you can do this with an external SSD if you have one available to use.

I ran the Apple HW Diagnostic Test and it said no issues found.

I'm not sure I want to try defusing the drive - can it be fused again?

 

[Juicy Box]

I'm not sure I want to try defusing the drive - can it be fused again?

Yes, assuming your drives work.

Actually, you can fuse any two drives, even two SSDs, even one internal and one external, or even two external drives.

You use terminal to fuse and de-fuse, which can be intimidating for some, but the inputs can be copied and pasted.

 

[Juicy Box]

Or, just use an external SSD.

 

[Mlrollin91]

Or, just use an external SSD.

This. My wife has a 2019 21.5" iMac with a 1TB Fushion drive, we got a Samsung T7 1TB external and its night and day. The computer is actually usable again.

 

[jbmillard]

This. My wife has a 2019 21.5" iMac with a 1TB Fushion drive, we got a Samsung T7 1TB external and its night and day. The computer is actually usable again.

I don't doubt it, but I want to make sure I understand the problem before I start purchasing hardware.

 

[jbmillard]

Yes, assuming your drives work.

Actually, you can fuse any two drives, even two SSDs, even one internal and one external, or even two external drives.

You use terminal to fuse and de-fuse, which can be intimidating for some, but the inputs can be copied and pasted.

Command line doesn't bother me. I'll try and defuse the drives and install Monterey and see if works better.

 

[jbmillard]

Yes, assuming your drives work.

Actually, you can fuse any two drives, even two SSDs, even one internal and one external, or even two external drives.

You use terminal to fuse and de-fuse, which can be intimidating for some, but the inputs can be copied and pasted.

I've not found anything on defusing two drives. Do you have a link to the procedure?

 

[rpmurray]

Don't know if this will help you, because it sounds like it would take on the back end of forever to install a new app, but you could try installing something like DriveDX (it has a free trial) and have it do a diagnostic on the Fusion drive. Fusion can be a world of hurt if either the SSD or the HD that make up the drive start to fail.

I agree with those above that it sounds like some part of the drive is starting to fail. BTW, Apple Hardware Diagnostics is usually pretty worthless in actual diagnosing hardware problems. Usually it will only report a problem when the component has already failed, but up to that point will tell you it's OK, no problems found.

 

[casperes1996]

I've not found anything on defusing two drives. Do you have a link to the procedure?

How to split up a Fusion Drive

Whether you made your own Fusion Drive and want to go back, or want to split up one you got from Apple, we'll show you that it isn't a difficult or lengthy process.

www.macworld.com

When you want to refuse you can just google "fix split fusion drive" or create fusion drive

 

[jbmillard]

How to split up a Fusion Drive

Whether you made your own Fusion Drive and want to go back, or want to split up one you got from Apple, we'll show you that it isn't a difficult or lengthy process.

www.macworld.com

When you want to refuse you can just google "fix split fusion drive" or create fusion drive

Thanks, I found the article on fixing split fusion drives - but I didn't see this.

 

[jbmillard]

Unfortunately, the defuse procedure says that it wipes the recovery partition (I'll admit that I am not an expert here, but that sounds like I then can only install over a network) which I'm not comfortable doing at the moment. Hopefully I can get DriveDX running and see what it says.

 

[NSMacGuru]

Dollars to donuts it's the drive. But - could also be a few other things, like a wonky USB device. Do all your testing with a bare machine.

Presuming you have a bootable backup (you *do* have a bootable backup, right?) see if it performs better than booting from the internal (restart, hold down OPTION after the startup chime is heard, select the drive you want).

FWIW, I'm on a custom-build 2017 iMac (purchased in 2019 just before the new models arrived, sigh) and also have that crappy Fusion drive.

For the past month I've been running Ventura off of an external 3.5" Barracuda in a two-bay dock connected via USB-3, and the performance has been at least equal to what I was seeing with the internal drive (yea, I'm surprised too).

Booting from an external is a pretty quick diagnostic to indicate whether your internal drive is pooched.

 

[jbmillard]

Dollars to donuts it's the drive. But - could also be a few other things, like a wonky USB device. Do all your testing with a bare machine.

Presuming you have a bootable backup (you *do* have a bootable backup, right?) see if it performs better than booting from the internal (restart, hold down OPTION after the startup chime is heard, select the drive you want).

FWIW, I'm on a custom-build 2017 iMac (purchased in 2019 just before the new models arrived, sigh) and also have that crappy Fusion drive.

For the past month I've been running Ventura off of an external 3.5" Barracuda in a two-bay dock connected via USB-3, and the performance has been at least equal to what I was seeing with the internal drive (yea, I'm surprised too).

Booting from an external is a pretty quick diagnostic to indicate whether your internal drive is pooched.

Everything has been unplugged from the computer except the keyboard. I have backups, but not bootable backups.

 

[jbmillard]

It only took about three hours to get it to run, but here's the output of DriveDX. Doesn't look good.

Is it worth trying to boot Monterey off of a thumb drive to see if it's better? I'm concerned the data rate of a thumb drive won't be much better. I'll have to see if I have any external drives around here. I might.

 

[ValkyrieStudio]

I am an incredible lurker here, but I saw this thread and realized it was the thread I was born to answer. Well, potentially.

I had what sounds like a very, very similar thing, and my 2019 iMac is very similar to yours. I did all of this. ALL of it. Reinstalling, reformatting, recovery mode, took to an Apple store, moved RAM sticks, talked to an Apple specialist every day for over a week, submitted diagnostic reports, nothing was really showing anything amiss.

By some random fortune, SOMETHING we did diagnosing made me curious about something I hadn't seen in Activity Monitor - it wasn't using a lot of CPU, often, but it was popping up just here and there and I looked it up. I'm sorry that I forgot the process name, but the point is that it was tied to Spotlight and indexing. The rep and I had tried a thing where we disabled Spotlight but it wasn't the solution.

In the end, a tiny thread on Reddit had the answer - I have Boot Camp installed, and something during one of the Monterey patches changed SOMETHING and every time Spotlight tried to even look at my Boot Camp partition, this happened. Freezing, crashes, apps being unresponsive for 5-10 minutes at a time.

So after over a month of trying things and going to stores and everything else... the solution was to just open the Spotlight preferences pane, add my Boot Camp drive to the "privacy" section to cause it to stop trying to scan it, and 100% of my issues went away immediately, and months later, have never resurfaced. I don't know if they fixed this in later Monterey patches or Ventura, but I'm not itching to test, haha.

Now, as I was typing this you posted and you do have physical drive issues, and, alas, I took too long to share this, haha. So maybe this won't help at all, but since so, so much of this was what I went through, I wanted to share the solution in case it can still help you (or anyone reading this).

 

[now i see it]

Everyone should have a bootable external SSD handy. It’s required equipment as far as I’m concerned when using a Mac.

 

[jbmillard]

So after over a month of trying things and going to stores and everything else... the solution was to just open the Spotlight preferences pane, add my Boot Camp drive to the "privacy" section to cause it to stop trying to scan it, and 100% of my issues went away immediately, and months later, have never resurfaced. I don't know if they fixed this in later Monterey patches or Ventura, but I'm not itching to test, haha.

Thanks for the input. I've not used bootcamp so I don't think this is it.

 

[Fraserh02]

I am curious.. why did you create this spec computer? It’s all so high tech for the time except for the sometimes damn slow Fusion Drive. Wouldn’t it have made sense to of got say the 256/512GB with an external 3TB hard drive for the same price? Likely would have maybe not had this issue. I’m not massively glued up but couldn’t it be a failing HDD or even the 28GB SSD portion has started to fail because it has to transfer data between it frequently to store you most used apps. Fusion drives work by using the small SSD for OS boot and as a type of swap for fast access to files and apps used often. Maybe it’s came to its end of writes?

 

[jbmillard]

I am curious.. why did you create this spec computer? It’s all so high tech for the time except for the sometimes damn slow Fusion Drive. Wouldn’t it have made sense to of got say the 256/512GB with an external 3TB hard drive for the same price? Likely would have maybe not had this issue. I’m not massively glued up but couldn’t it be a failing HDD or even the 28GB SSD portion has started to fail because it has to transfer data between it frequently to store you most used apps. Fusion drives work by using the small SSD for OS boot and as a type of swap for fast access to files and apps used often. Maybe it’s came to its end of writes?

Until now, I've not had any problem with the fusion drives. The iMac I'm typing this on is 7 years old. No issues with speed. I upgraded the processor and RAM because I run VMs for development and it's nice to be able to allocate 16 GB or so to each VM.

DriveDX says the SSD is fine.

 

[allan.nyholm]

Suggestion here is to use the SSD drive exclusively. As you've probably gathered so far try getting a second SSD - either a stock ssd and a companion Thunderbolt / USB 3 case and use that for your OS. But seeing that your SSD drive is fine and you have a 3TB Fusion Drive then I'd use that internal SSD over an external one.

And try experimenting with having your VM's on an external SSD.

My own situation is that while my internal harddisk drive is in tip top shape I don't use it for anything but a 2nd Time Machine drive. I have resorted to only using external Thunderbolt and USB devices. And my iMac is even older and didn't come with a Fusion Drive because I was buying the low-end model

 

[jbmillard]

Suggestion here is to use the SSD drive exclusively. As you've probably gathered so far try getting a second SSD - either a stock ssd and a companion Thunderbolt / USB 3 case and use that for your OS. But seeing that your SSD drive is fine and you have a 3TB Fusion Drive then I'd use that internal SSD over an external one.

And try experimenting with having your VM's on an external SSD.

My own situation is that while my internal harddisk drive is in tip top shape I don't use it for anything but a 2nd Time Machine drive. I have resorted to only using external Thunderbolt and USB devices. And my iMac is even older and didn't come with a Fusion Drive because I was buying the low-end model

I'll probably replace the internal hard drive with an SSD so external will be a moot point.

 

[profcutter]

Yeah, fusion drives are notoriously flaky, some work without issue for as long as you want, some start to get sick and then die, and some die without warning. I'd second the external SSD, it will be much faster than simply adding a SATA SSD internally, unless you were already planning on doing the blade drive. It also saves you the trouble of taking the machine apart. If you really want to open up the machine, then replacing the AHCI SSD is the best way to go.

 

[Isamilis]

View attachment 2131491
It only took about three hours to get it to run, but here's the output of DriveDX. Doesn't look good.

Is it worth trying to boot Monterey off of a thumb drive to see if it's better? I'm concerned the data rate of a thumb drive won't be much better. I'll have to see if I have any external drives around here. I might.

It’s been clear, the issues are on the boot disk. “Simple” solution (IMO):
1. Buy the external SSD (I used Samsung T5) for bootable disk. Attach it to the back of iMac screen (I used 3m double tape)
2. Install the Os on the external SSD
3. Check if the problem remains (very unlikely)
4. Reformat the original disk, check whether any parts of it are still usable (whether you can store the data safely)
5. You can restore or replace the original disk (I don’t know whether this is possible for your iMac). The replacement disk shouldn’t have to be your bootable disk (since you have one anyway). It also can be non-SSD (cheaper) because all the swap and temporary files are already in the new external SSD.
6. Other option, the new external SSD (in step 1) - get bigger capacity (around 3Tb to match with the original disk)

Add: answering your question. It’s not worth to try with other (newer) OS. Failed disk will be worsen on the newer OS (due to they are more complex - need more ram, more swap, more cpu etc).