Why is my iMac 27 running slow after the latest update

I'm late to party, but allow me to add a couple of thoughts. I agree its probably time for a newer Mac but there may be value in the diagnostic process to avoid similar issues with a newer one, especially if your current issues involve third-party hardware or software.

—You said this started yesterday. Did anything change yesterday? Devices added? Cables changed? SW installs?Etc.

—You have some apps that must "phone hone." Have you tested your internet speed?

—You have Apple's Fusion drive. To me, this data:

Performance:

System Load: 1.45 (1 min ago) 1.11 (5 min ago) 1.30 (15 min ago)

Nominal I/O usage: 0.07 MB/s

File system: 26.57 seconds

Write speed: 591 MB/s

Read speed: 2631 MB/s

does not scream a sick drive. In your iMac model, and based on a lot of Etrecheck drive reports here, expected Fusion performance for a healthy drive is:

• Writes between 600-900MB/sec
• Reads as high as 2000MB/sec.

Your Writes are at the bottom end of the range but close enough to normal. Your Reads are far above expected. A File System score of under about 40 seconds is what one sees for a healthy drive system. Yours did it in 27 seconds.

This is the same EtreCheck data from my 18,3 2017 5K iMac with a 4.2gHz i7 processor and Apple's factory 1TB SSD:

Performance:

    System Load: 1.66 (1 min ago) 1.42 (5 min ago) 1.31 (15 min ago)

    Nominal I/O speed: 0.23 MB/s

    File system: 20.35 seconds

    Write speed:  2156 MB/s

    Read speed:  2863 MB/s

Pure SSD systems always have faster Writes than Fusion but look how well your Reads compare to a factory SSD.

Is 600MB/sec slow? Well, I have a much earlier Macbook Pro I retrofitted with an old-school SATA 6 SSD. Both its drive scores are just under 500MB/sec and it never feels slow in use.

I can't help but think there is something else contributing to your "slows."

—A very easy test for a possible suspect is to disconnect all USB externals except for your mouse and keyboard, then run a while and see if your Writes score increases. I am seeing issues with older USB devices like USB2 mixed with current devices affecting performance. A USB 3 device connected with a USB 2 cable or hub will run at USB2 speeds.

If performance improves, then reconnect devices one by one to see when speeds drops again.

—Is the Samsung external SSD used as a simple backup disk or something more demanding, like a scratch disk or a boot helper?

—It looks like Cocktail is installed. If so, try disabling it and testing,

—Evict any apps that claim to "clean," etc.

I have no quibble with the others' recommendations but think it would be prudent to know what has slowed this Mac so you can be aware of such issues in the future if it turns out to be a third-party product causing it..

If you suspect the HD, download and use DriveDX (the eval version is fine) and carefully examine the report on the HD. If ANY errors appear that only confirms the HD is failing. That means it's time to either replace the HD (I'd get an SSD if you are going to go that route) and have an Apple Authorized Service Provider do the work. Or, you may be wise to simply buy a new Mac mini based on the M4 chip with a 1TB Ssd and your machine will far outperform you iMac.

That’s not because intel chip , iMac 27 inches has mechanical HDD that’s the reason is running slow , if you replace the HDD for SSD and increase the ram to 64gb your iMac will runs faster , I have two one in 21.5 and other in 27 inches boths runs faster than before with a SSD

This may be due to the fact that your Mac is still running off of Intel hardware, and how Apple purposefully puts software "buffers" as their computers get older in order to keep their components in check. I suggest contacting Apple Support.

No current Macs are upgradeable EXCEPT the Mac Pro. The last time a user could upgrade RAM on an iMac was the 2020 27" machine, iMacs made in 2021 and beyond are not user upgradeable. So when selecting a new Mac, take your time and select one the suits your needs now for the foreseeable future. If your use is is that of a typical user meaning:

• Email
• Web surfing
• Using productivity apps such as MS Word, Excel, PowerPoint etc..
• Light photo editing

Then a base Mac mini with 16GB of RAM and a 1TB SSD is fine. However, if you are a professional or gamer then buy additional RAM.

No current Macs are upgradeable EXCEPT the Mac Pro. The last time a user could upgrade RAM on an iMac was the 2020 27" machine, iMacs made in 2021 and beyond are not user upgradeable. So when selecting a new Mac, take your time and select one the suits your needs now for the foreseeable future. If your use is is that of a typical user meaning:

• Email
• Web surfing
• Using productivity apps such as MS Word, Excel, PowerPoint etc..
• Light photo editing

Then a base Mac mini with 16GB of RAM and a 1TB SSD is fine. However, if you are a professional or gamer then buy additional RAM. Do not scrimp on storage, as a general rule of thumb if the old Mac has a 1 TB drive, the new Mac should have that or more.

Also, if you decide to buy a new Mac (doesn't matter what Mac it is) to migrate your data from the old Mac please follow the instructions below:

·       Always connect your old Mac's Time Machine External Hard Disk prior to startup, this will allow a migration from your TM backup and it will be dead simple! When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes and follow the on-screen prompts and it's done! It is that simple! This is the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. 

·       NOTE 1: You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less. Something like: 

·       NOTE 2: If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts.

·       The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps), data files & settings. They do not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not an issue. 

Finally, my recommendation is not using Wi-Fi when doing Setup Assistant or Migration Assistant. Why, it simply fails in a lot of the cases reported in these forums. A wired connection is more reliable and the last thing you need is a failed migration when there are safe methods readily available. Please read and follow the directions in Setup Assistant and Migration Assistant. If you do not have a Time Machine backup of the older Mac then create one!If you are not aware of Time Machine, please read Back up your Mac with Time Machine and finally if you need an External Hard Disk to use as a Time Machine External Hard Disk then many experience users on these forums prefer the OWC Mercury Elite Pro due to it's reasonable price, high level of quality and ease of use. 

Great on using Carbon Copy Cloner, it's a great app. If your are a heavy user of Lightroom, Photoshop & Topaz then on a MM I'd recommend 24GB of RAM. By the way, you also may benefit from using Mac - Which Mac is best for me? - Apple