iMac 2019 experiencing slow startup and app issues

How to fix a split Fusion Drive - Apple Support

❝ If you're not sure that your Mac was configured with a Fusion Drive, or that the drive has been split, disconnect any external storage devices from your Mac, then open the storage overview:

• In macOS Ventura or later, choose Apple menu  > System Settings. Click General in the sidebar, then click Storage on the right.
• In earlier versions of macOS, choose Apple menu  > About This Mac. Then click Storage. 

If you see a drive labeled Fusion Drive, your Fusion Drive is working and this article doesn't apply to you.

If you have a Fusion Drive that has been split, you should see two drives. One of them should be labeled Flash Storage, with a capacity of 24GB, 32GB, or 128GB. The other should be at least 1TB. ❞

I also checked the Read/Write speeds of the Fusion Drive after my colleague @HWTech’s comments.

I’m not an expert in Drive Performance Levels, but I’ve experimented with the exact model, configuration, and Read/Write values from the report.

I ran it through an AL/LMM Model to see what it had to say.

So, what follows should not be considered an authoritative basis for a definitive answer, but rather an indicator of the current state.

I suggest you follow the previous suggestion from my colleague @D.I.Johnson 👍 and use an external drive as your bootable drive if you want to extend the life of this computer. 

Drive Performance Evaluation - AI / LMM evaluation 

Write Speed: 340 MB/s

Rating: Fair / Below average

For a Fusion Drive, this write speed indicates the system is mostly writing to the SSD cache, which is expected. However:

• Modern SSDs write at 500–3000 MB/s
• Even SATA SSDs write at 450–550 MB/s

340 MB/s = slower than SSD, faster than HDD, but not “good.”

Read Speed: 1446 MB/s

Rating: Good (for this setup), but misleading

This high read speed indicates that the test hit the SSD portion of the Fusion Drive.

The 28 GB SSD is much faster than the HDD, so your read test did not reflect the slow part of the drive.

Important:

• Reads from the HDD portion would only be 120–180 MB/s.
• So the Fusion Drive feels fast only when the data happens to be on the SSD.

1446 MB/s = SSD-only result, not representative of full Fusion Drive performance.

File System Response Time: 22.79 seconds

Rating: ❌ Very bad

This is the most important number.

A healthy system usually has:

• 0.1–1.0 seconds under normal load
• 2–5 seconds under strain

22.79 seconds = severe I/O delays, typically caused by:

• The HDD portion being overloaded
• The Fusion Drive shuffling data between the SSD and HDD
• RAM pressure forcing swap to the HDD
• Spotlight / Photos / iCloud indexing hammering the HDD

This indicates the HDD is the bottleneck and overall drive performance is poor.

Replacing the HD in your Mac is one option. It involves at least a partial teardown of the computer to get the job done and has some risk.

Another, much simpler option is to connect an external drive to a Thunderbolt/USB3 port, install macOS on that and use it as the startup device to run your Mac. Much less expensive than option 1 and zero risk of doing internal damage to the computer.

This is Apple’s guidance on how to: Install macOS on an external storage device and use it as a startup disk - Apple Support

Please also see this great user authored tip: Use an external SSD as your startup disk - Apple Community (Thanks, Jack-19!)

A third option is replacement of the whole computer.

There are 2 iMacs from 2019

iMac (Retina 4K, 21.5-inch, 2019) - Technical Specifications

iMac (Retina 5K, 27-inch, 2019) - Technical Specifications

In either case, suggest disconnecting any and all external drives

Then, restart the computer

Does the machine boot up any faster

If not >>

Part 1 of 2

Restart the computer in Safe Mode 

Do the issues persist ?

Sometimes a Safe Boot followed by a Normal Boot will just put things right.

If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

Part 2 of 2

To Drill Down further and to avoid a session of Q&A, Q&A  and Q&A  

Download the Application Etrecheck  ( External Link ) directly from the Developer.

The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 

This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

Please read my previous post.....I asked for you to post the complete DriveDx text report....you only posted a screenshot of the summary for the SSD.

When you click on the first "Macintosh HD" item in DriveDx, you will see the "Save Report..." button at the top right of the DriveDx window which will save the report for that physical drive as a text file.....which apparently is for the SSD portion of the Fusion Drive.

When you click on the second "Macintosh HD" item in DriveDx, you will want to "Save Report...." again to save the complete text report for the 2nd drive which apparently is the Hard Drive portion of your Fusion Drive.

You will want to copy everything from each resulting saved text report file & paste it into the "Additional Text" field. The report for the Hard Drive is the most important since the SSD is unlikely to be the problem.

For a long time now re-starting my iMac takes 30 minutes or longer.

This is a common symptom of a failing hard drive. Be sure you have an up-to-date back up.

You can confirm a Fusion Drive has split by checking how the drives appear in Finder or System Settings/Disk Utility, which will show two separate drives instead of a single one.

A split drive will be visible as a "Flash Storage" drive and a larger capacity drive (usually 1TB or more), rather than a single volume labeled "Fusion Drive". 

Unsigned files - There are unsigned software files installed. These files could be old, incompatible, and cause problems. They should be reviewed.

System modifications - There are a large number of system modifications running in the background.

Runaway user process - A user process is using a large percentage of your CPU.

There's software installed dating back 2007, 2013, 2011, 2019, 2017 etc

Added to all this is, an un-need Malwarebytes and Google Chrome

Both of which are known to be CPU and Memory Hogs

Check you OTHER posting and then post the DriveDx report in this question

Cannot scroll down in first post - Apple Community

A very quick look 👀 - ok

Regarding a Fusion Drive

Yes it is a Fusion Drive

APPLE HDD ST1000DM003 1.00 TB (Mechanical - 7200 RPM)

disk1 - APPLE SSD SM0032L 28.00 GB (Solid State - TRIM: Yes)

Though, it appears NOT to be Split drive which is good news

allenz wrote:

Thanks. I'm familiar with Etrecheck.

Only 1 external drive but it's turned off. Only stors some old video ediding stuff I used to do.

I'll print your reply and report back. Hopefully I cn get it done this weekend.

Thanks again

Allen

You are welcome

When time permits from you end

We are usually around most days to lend assistance

D.I. Johnson wrote:

Owl-53 wrote:

Sorry if I butt in here

But is it not a bit premature to arrive at the conclusion the Drive has failed

Agree.

Probably getting ahead of things here.

Carry on. 🙂

Not at ALL my friend 👍

Very reasonable and possible the drive itself is kaput

In which case your suggestions would be a brilliant solution 😎

I would wait for @ HWTech to review the Drive Dx reports as they are far more knowledgeable with this application

From an inexperienced user like me and the results of Drive Dx

I would say the drivers are ok

The real issue from perspective is what has been installed and used on the machine is a primary root cause of the issues