iMac (Late 2012) Performance Issues : External SSD via TB2?

-g wrote:

2012 has USB3 -- correct?

The late 2012 iMac has 4 x USB 3.0 ports.

Using TB2 would very costly, given that it is now old technology and would be of very limited (no?) use on newer machines.

In fact, unless Daveidic has a good reason for wanting to keep this Mac running (e.g., mission critical old software), one might simply wish to invest in a newer Mac. If I was doing this (and I have done it actually), I would just buy a SSD in a USB external drive and then run the system off that. When it comes time to buy a newer Mac the SSD could be used with that as a backup (I use my old drives as backups with my new iMac).

The internal Hard Drive is a problem. That Load Cycle Count RAW value is over 2 million.....most drives have a limit of 800-900K.....some even as low as 250K....all depends on the drive and Seagate 2.5" HDs tend to have a much lower limit although this appears to be a HD from 2012 which may allow for a bit more than 250K Load Cycles.

When the Load Cycle Count exceeds the manufacturer's expectations, then the HD will experience performance issues and possibly very odd behaviors. You definitely cannot trust that internal HD anymore. It is unfortunate that macOS is so aggressive these days with the sleep & wake cycles which is what has killed that internal HD, but all Apple cares about are SSDs and they forget some people were still using HDs in their setups.

Your best option is to boot from an external SSD. Even a USB3 SSD will give you better performance than you are now getting since a USB3 SSD can achieve about 500MB/s transfer rates (assuming a good SSD....some SSDs can be even slower than your iMac's current performance).

CleanMyMacs strikes again. It considered by many here as BrickMyMac. Get the drift?

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.  

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).  

Additionally, a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

My recommendation is to remove CMM according to the developer's instructions and verify the supporting files are gone also by using  Find Any File by searching for and deleting any searched files that come up when you search in Find Any File;

1 - Name contains cleanmymac

2 - Name contains macpaw

Also the HDD portion of the Fusion Drive may be failing. Download and run the free version of DriveDX and post the results here.

Is the 1T HDD to only drive that DriveDX sees..?

If you have a Fusion Drive, then DriveDX should also see an SSD.

In addition to DriveDX, please run and post an EtreCheckPro report.

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post back here with your Report, as per > How to use the Add Text Feature When Post… - Apple Community

If you want to use an external SSD as a startup disk for the Late 2012 iMac, then a 2.5" SATA SSD in a USB 3.0 enclosure is your best bet.

Daviedic wrote:

iCould an external SSD that I can connect via the Thunderbolt 2 port be an option, if so what would be a good buy ?

Not a good option. Thunderbolt 1 and 2 lived on the Mini DisplayPort connector – unlike Thunderbolt 3, 4, and 5, which live on the USB-C one. Nobody makes Thunderbolt 1 and 2 accessories any more.

You'd need something like this no-longer-available OWC Thunderbolt Dock Solution (which cost $220 when you could buy it) just to have a place to plug in your SSD. (You might be able to "roll your own" docking setup, using Apple's TB 3-to-2 adapter and a powered Thunderbolt 3 dock.)

You'd also have to be careful not to buy any Thunderbolt 4 or 5 equipment, as Thunderbolt 4 and 5 accessories aren't backwards-compatible with Thunderbolt 1 and 2 hosts.

And, of course, since Thunderbolt 2 is slower than Thunderbolt 3, any Thunderbolt 3 SSD that you attached this way would potentially be bottlenecked by Thunderbolt 2.

Good work posing those reports.

For starters:

1) Uninstall all traces of the Avira-ware as per the developers directions.

2) Turn off the active scan feature of Malwarebytes and only occasionally run it manually.

Then startup in Safe Mode followed by a normal restart and test.

see > Start up your Mac in safe mode - Apple Support

EtreCheck Pro is also showing a Write/Read performance issue with your Fusion Drive.

After removing the Avira-ware, turning off Malwarebytes and using Safe Mode, run a new EtreCheckPro report.

If the new EtreCheckPro report shows a large Write/Read improvement, then run the iMac for a while longer.

If not, then run the iMac from an external SSD for a while longer or until you can replace it with a new Mac.

Conceivably your slow down could be related to How to fix a split Fusion Drive - Apple Support

Exchanging the internal drive is a decidedly not-fun activity since it involves taking off the display. Booting off an external SSD would likely be easier. The problem then becomes finding a TB2 enclosure. I see a few online but at several hundred dollars you're probably thinking a good portion of simply getting new Mac where everything would be faster (I replaced my 2012 iMac with a M4 mini). I booted my late 2012 iMac over USB3 (the ports are only USB 3.0) and it wasn't too bad in terms of speed, given that anything on a 14 year old Mac is going to be slow by modern standards.

Don't use a cleaning tool. It alone could be a reason why you are seeing poor performance.

2012 has USB3 -- correct?

if you choose to move your boot system over to an EXTERNAL -- and not do the internal recommendations

i would go with a USB3 enclosure -- SATA SSD -- over Thunderbolt2

TB2 is end of life (not supported on newer machines)

but do the separation and reformatting of the Fusion drives -- that may bring them back to reliability -- if you are okay with their performance -- just re-fuse and reinstall macOS> Migration Assistant...

driveDX app will offer a big clue what's going on with your drives

BlackMagic and AJA speed apps will offer you another clue -- your drives' Read/Write speeds MBs

i prefer faster...fusion is slow

Servant of Cats >> Depends on the Fusion Drive.

i'm talking about Apple so-called "Fusion" drive configuration

Apple (2017-2019) fusion configurations are typically 3 percent NVMe SSD -- 97 percent HDD (spinning hard drive, capable of 80MBs read/write max sustained "speed") -- i never followed fusion on earlier years

in my opinion, 80MBs is slow -- with or without "pushing" the system to the 89-97% 5400RPM hard drive

i will argue the "speed" of fusion technology is an illusion -- under load

albeit, fusion does greatly reduce boot times, and some tasks

it is still 89-97 percent HDD, 5400RPM, limited to 80MBs

an external USB3 SSD enclosure will perform five times faster than HDD -- SATA SSD in a USB3 enclosure would be my choice over fusion drives on 2012 hardware (if i didn't have the skill or budget to upgrade or REPAIR the internal HDD to SATA SSD)

fusion may be great for some users -- my time (and pleasant user experience) are more valuable

i'm saying

>> any suggestions!

run DriveDX to scan your drives for health issues

there is a free trial period

(DriveDX may identify the problem outright, ie your drives are failing)

BACKUP boot system/user to Clone (i use Carbon Copy Cloner app) AND TimeMachine external drives

separate (de-fuse) and Erase/reformat the internal Fusion ssd/hdd

cut the screen off the machine

blow out the dust

Swap the HDD with a Samsung 870 EVO SATA SSD

And Erase it (the new Samsung), APFS format

don't re-fuse the SSDs

leave the the Apple SSD in place if you don't have the experience to remove or upgrade it

install the macOS on the SATA SSD (Samsung)

use Migration Assistant to bring over your backup stuff...

+++++

AVOID ANY CLEANER-TYPE APPS -- they may be great if you are an expert with them, but bad news in my experience

-g wrote:

i prefer faster...fusion is slow

Depends on the Fusion Drive.

There are a couple of issues:

• By the time that Fusion Drives appeared, 21.5" iMacs had lost their optical drives and gotten really thin. There was no longer room inside for a 7200 rpm 3.5" desktop hard drive (as on the 27" models), so 21.5" iMacs with Fusion Drives were equipped with slower 5400 rpm 2.5" notebook hard drives.
• Starting in Late 2015, Apple drastically cut the amount of flash (SSD) space included with 1 TB Fusion Drives. The original 1 TB Fusion Drives had 128 GB of flash. The later ones had 24 – 32 GB of flash. This was "prime real estate", but there was not nearly enough of it.

The 1 TB Fusion Drive in the OP's 2012 iMac would have a 5400 rpm notebook hard drive combined with 128 GB of flash (SSD) space. That 128 GB should be enough to help performance unless the Mac is being pushed really hard.

The report indicates that your drive is beginning to fail:

Failing Indicators (life-span / pre-fail) : 0 (0 / 0)

Warnings (life-span / pre-fail) : 0 (0 / 0)

Recently failed Self-tests (Short / Full) : 0 (0 / 0)

I/O Error Count

as does the Etrecheck report. You should get a Time Machine backup of your drive ASAP and plan on getting a new Mac.

May I suggest a replacement: a 10 Core Mac Mini M4 with 16 GB RAM and 1 TB SSD ($1084 US) with a 32" LG 4k monitor ($331 US) from Amazon.com)  is $1415 US which is $541US less than a similarly configured new 24" iMac ($1956 US)  re 07/2025. Keep your keyboard and mouse from your current Mac for use with the Mini. 

I got the above Mini with a 32" LG 4K monitor w/speakers for only $60 US more than the 27" (didn't know the Mini had a speaker).  There are many monitors available in 27" size on up for $100 US to $500 US depending on what features you want.  The monitor prices are before tariffs.

Just some food for thought.