Slow 2019 iMac with Fusion Drive

The first thing I noticed is that you purchased the slowest iMac, 8 GB or RAM and a 540i0 rpm hard drive in the fusion drive.

Secondly, you've installed software that most of the experienced users here consider akin to malware, CleanMyMac.

Yhere is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

So uninstall CMM according to the developer's instructions. You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For CMM software you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Name contains macpaw

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

Here's hoping that you get your iMac back to the speeds you have initially.

You've installed some "junk" ware that most of the experienced users here consider to be akin to malware: CleanMyMac.

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

That being said uninstall CleanMyMac according to the developer's instructions. You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For CleanMyMac software you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Name contains macpaw

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

Remember that you've purchased the second slowest Mac Apple offered at the time of purchase: 8 GB RAM and a 5400 rpm Fusion drive. So the fewer apps you have running in the background all the time (i.e. User Login Items) the better.

Hey Servant of Cats, is there a way for me to tell if the computer is using the HD portion of the drive

It is definitely using the HD portion of your drive. The EtreCheck report shows 460.86 GB used on the Macintosh HD – Data volume, and another ~15 GB for other volumes. That's not all going to fit on the 28 GB SSD.

I thought that if I ran EtreCheck while using multiple applications (like Photoshop and InDesign) that it might give me a different reading on disk speed. But on each report disk speed has remained very fast.

The reason that testing reports a fast disk speed is two-fold. The Mac uses part of the SSD component of the Fusion Drive as a write cache. If the data that you write out is small enough to fit in the free part of that cache, then the write "completes" when the data is in the cache. The Mac may decide that the data should live on the HDD, in which case there is a slower background transfer from the SSD to the HDD.

The Mac also uses the SSD to store portions of files that it thinks are going to be read frequently. An educated guess is that much of the coveted SSD space gets filled up with pieces of macOS itself, and with pieces of the applications that you launch most frequently.

The data in the write cache is also on the SSD – so if a disk speed test application writes a bunch of data which fits into the cache, then reads the data back right away, guess what? The data is probably still in the SSD cache where the read speeds are very high.

This is all a probabilities game. Where it breaks down is

• If there is not enough room in the SSD to store (pieces) of files that the system frequently uses. (Needing to go to the HDD for a file that you read or write infrequently, like a full-size photo, is much less painful than having to go to the HDD for one that the system beats on constantly, like the Lightroom catalog.)
• If you're writing a lot of data quickly, so that you fill up the write cache before the system has a chance to make room in it by transferring data to the HDD.

I'm guessing that you're not really pushing the limits of the write cache. So EtreCheck and other disk speed test programs wind up testing the speed of the SSD write cache, even when you're running other applications.

But your Mac's Fusion Drive only has 28 GB of SSD space. It seems very likely that the part that is not set aside for a write cache is not big enough to hold all of the macOS and application files which would really benefit from the SSD's speed. Your system ends up having to go to the HDD for some very-frequently-used files … and that slows startup times and reduces overall performance.

If your Fusion Drive had 128 GB of SSD space – like the original Fusion Drives did – we might not be having this conversation. But you're stuck with a 28 GB SSD and a 5400 rpm HDD. Which is why I think that even a "slow" USB3 / SATA startup SSD might, overall, offer better performance than your Fusion Drive.

Note that your 2019 iMac has two USB-C (Thunderbolt 3) ports. That means that if you wanted, you could use something faster than a USB3 / SATA SSD.

For instance, here's a portable SSD that runs at faster-than-USB3 speed, but can work with just about any Mac that has a USB-A or USB-C port. 1 TB for $130. There are Thunderbolt 3 SSDs that run even faster – but those cost more.

https://eshop.macsales.com/shop/owc-envoy-pro-elektron

Hi there, Nugget1989, I'm no expert and I sure don't work for Apple (nobody does here, we're all just Mac users here same as you)

two things stand out for me----

One, you have just the bare minimum of RAM (memory) to run the operating system, more RAM (memory would sure help you out a lot.... according to this link,https://eshop.macsales.com/shop/apple/memory/iMac and the model number/screen size of your iMac, you could have either 64 Gigs (GB) or 128 Gigs (GB) MAX...the 64 gigs will run you about $145 USD and the 128 gigs will run you about $250 USD.... (plus shipping and taxes, of course)

you'd need to contact your local AASP (apple Authorized Service Provider) or Apple Store with Genius Bar, make an appointment with either one of them, and take your iMac in to have the RAM (memory upgraded) . this is NOT something the average user can do at all. (or an experienced one, for that matter) . DO you have, are you using regularly, a Time Machine backup ?? it's smart, good practise and insurance to have and use a Time Machine backup regularly..... I'd also run Disk Utility and check on the status/health of your internal (built in )Fusion Drive...

Sadly, 99% of all hard drives/storage drives can, do, and will fail/die (in time) --usually, unexpectedly and without much warning if at all... and without a backup of your Mac, you could be in a lot of trouble.....you could, after setting up/enabling, getting going and doing a Time Machine backup, regularly, then verifying it... also get your AASP or Apple Store with Genius Bar to back up your stuff, and swap out your internal Fusion Drive with an SSD of the same or greater capacity/size than your current one... SSD's are known to be much faster than conventional hard drives, even Fusion Drives, for accessing and writing data... their only downside is that they are more expensive.... and may not be available in huge capacity/size.... I don't know what the max size (absolute biggest) is for an SSD, but it's up there somewhere.... this site/link https://eshop.macsales.com/shop/ssd/owc/imac-21.5-inch/2013-2019 (again, same one as before, they are reputable and good vendors) says up to 4 TB capacity and size can be installed in either model (21" screen size or 27" screen size of an iMac from 2019) .... retail price on a 4 TB drive only is around $400-$450.... and, as always, if you're ordering online, and getting it delivered to you, you have to tack on shipping and taxes as well.... I don't know what your local AASP or Apple Store with genius Bar would charge for all of that...you'd have to contact 'em (give 'em a call) and see what they have to say....

hope this helps you....

good luck with the upgrade and the graphic designing....I think your iMac also supports eGPU''s, if you needed a little more graphical Oomph or horsepower......

John B

Virtual Memory Information:

Physical RAM: 8 GB

Free RAM: 57 MB

Used RAM: 4.47 GB

Cached files: 3.48 GB

Available RAM: 3.53 GB

Swap Used: 0 B

That is a good thing. Since you are not using Swap, then you really won't see any benefit to adding more RAM. But, you should continue to check that under real-world conditions. Launch the apps you typically use and see how much RAM you are using and if you start using Swap. Swap space is dedicated space on your hard drive that the computer allocates for memory when your usage exceeds the available RAM. It can slow things down especially if you have a slow hard drive or one that is nearly full. If you can get by with running only one or two apps at a time to keep your Swap use to zero, then RAM should not be an issue.

It appears that your Fusion Drive is one with a slow 5400 pm hard drive and an extremely small (28 GB) SSD.

You have 8 GB of RAM, and it might be nice if you had more, but my bet is on the Fusion Drive being a huge performance bottleneck.

I would definitely advise looking into an external SSD - even “just” a USB 3 / SATA one if you are on a budget.

P.S. - All Fusion Drives originally had 128 GB SSDs. Over the years, as SSDs got larger and cheaper, Apple should have increased the size of the SSD component of their Fusion Drives to match.

They never did. Instead, they cut the size of the SSDs in some 1 TB Fusion Drives to a mere 24-32 GB. On a Mac with 32+ GB of RAM, there was not even room in the Fusion Drive to let the computer go to sleep without having to use the hard disk…

First, don't bother hauling an iMac to an Apple Store. Apple Geniuses will not upgrade devices, only replace parts "in kind." If you now have 8GB now, they will only remove it and replace it with 8GB. No more. And that model does NOT have user-serviceable RAM. You have to cut into a sealed case and gut the computer to get to the RAM slots.

That leaves the Apple Authorized Service Provider and, per the Apple article on RAM upgrades, not all Apple Authorized Service Providers will do that work. Call ahead to verify they will even consider doing it. It is slow, delicate work and ones I've talked with say they have to charge two hours of labor at US$60-80/hour. That's before the cost of the RAM and the reseal kit. Some choose not to do such upgrades because they must charge the customer too much for too little gain.

Second, at the time of the test, your iMac was NOT starved for RAM. The new metrics, well "new" since 2013, are Pressure and Swap used. The indicator in the posted report that says RAM is not the issue is Swap Used which is zero in your case. You can use Activity Monitor to see the Memory Pressure. The 2013 memory management changes made macOS work much better with smaller amounts of RAM, so Memory Used is not longer a key metric.

Adding RAM almost never speeds up a Mac, in spite of what all the RAM vendors proclaim, and slow boots are NOT a RAM issue.

Third, Your Fusion drive is performing well, and at speeds appropriate to that iMac model based on other EtreCheck drive scores I've collected:

Write speed: 884 MB/s

Read speed: 1471 MB/s

In fact, your important Writes are faster than expected. Usually in 21.5-inch iMacs with Fusion drives, Writes are 600-800MB/sec.

...and am thinking of buying an external SSD to use as the startup disk ...

An external USB 3 SATA 6G SSD can do writes/reads no faster than 400MB/sec, meaning that would be a step in the wrong direction and a waste of money. The only external that would be faster than your current drive is a Thunderbolt 3 or 4 external, and they are not cheap, but stinkin' fast:

https://eshop.macsales.com/shop/owc-envoy-pro-fx

Fourth, you have remnants of CleanMyMac that must go. I've seen scores of Etrecheck report here where removing CMM improved drive scores by up to 40%. "Cleaning" apps WILL slow your computer because they interfere with elegant, automated self-maintenance routines you paid Apple to build into the OS. That alone could be the source of your slow boot times.

Catlike, Macs clean themselves with no outside help. Their even self-defrag their drives.

Re: “Write speed: 884 MB/s

Read speed: 1471 MB/s”

That is clearly based mostly on the SSD portion of the Fusion Drive, not on the HD portion, which is likely to be running at 100 MB/s (plus or minus, if even that).

if the OP’s workload is causing the Fusion Drive to frequently hit the limits of the small 28 GB SSD, then many of his actual I/O operations may occur at the internal HDD speed, which is much slower than what even a good USB 3 / SATA SSD could deliver.

I will also note that there are USB-C (USB 3.1 Gen 2) / PCIe NVMe SSDs that are faster than USB 3 / SATA ones and cheaper than Thunderbolt 3 ones. One of those might be the “sweet spot” for the OP in terms of price/performance (although I would suggest that the OP research the available options).

/Applications/Utilities/Activity Monitor.app can show you what your Memory usage is.