iMac 27'' Late 2012 Fusion Drive Failing Apple SSD

[The.Rob]

Hi there,

as stated in the title, I own a late 2012 Intel iMac 27'' fitted with a 3TB Fusion Drive (3TB HDD spinning rust + ~120GB Apple SSD). The Apple SSD is failing on me now - tested it with DriveDX and the Wear Levelling Count is at 0% which has been noticable in using the machine (freezes occasionally and is noticably slower in accessing even often used files). After weighing my options I came to the conclusion that buying an SSD and replacing the whole Fusion Drive with an internal SSD altogether would be the best option financially and speed-wise.

I do have a question though I am unclear about: I was thinking about just leaving the failing Apple SSD in the system and just not use it because it is just so damn hard to reach the damn thing. I asked a certified Apple technician if they could do the swap for me (less hassle for me) and they told me that leaving the drive in the system and not using it is a bad idea because it can fail and then damage the system. Did they just blankly lie to me? In my understanding of how the Fusion Drive works this is just an SSD (Flash Drive) used to cache often used files, no? How could that possibly damage the system when it's not used after I replace the Fusion Drive with an SSD? Note: I don't want to replace the HDD in the Fusion Drive with the SSD, I want to not have a Fusion Drive anymore and just use a new SSD from here on out.

Is it possible to just leave the Apple SSD in the system and not use it anymore without a problem? Is it maybe also possible to "deactivate" that drive while it's still in the system - this way it would just sit there in it's slot and wouldn't bother anyone (doubtful this is possible)?

Thanks in advance for your replies.

 

[Fishrrman]

Here's what I'd suggest (my opinion will be different from others)...

First, don't open the iMac.
Split the fusion drive apart (using terminal).
Leave the SSD "dead, but in place".
Continue to use the HDD, because it's still good.

Get an EXTERNAL USB3 SSD.
Set it up to be the "new boot drive".
It should have on it:
- the OS
- applications
- your basic accounts
Leave "large libraries" of movies, music and pics on the internal HDD (they don't "need speed").

I'd suggest either a 500gb or 1tb size for the external boot drive.
You can buy a "ready to go" drive (just plug it into a USB3 port)
or
Get a 2.5" "bare" SATA SSD of your choice (I like Crucial or Sandisk), and put it into an enclosure like this:

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free External Hard Drive Enclosure [Optimized for SSD, Support UASP SATA III] Black (EC-UASP)

SABRENT 2.5 Inch SATA to USB 3.0 Tool Free External Hard Drive Enclosure [Optimized for SSD, Support UASP SATA III] Black (EC-UASP)

tinyurl.com

(Just snaps together).

An external USB3 boot drive will be quite snappy, with reads in the 420-430MBps range.
You'll get used to the "2 drive icons" on the desktop.

 

[Juicy Box]

Did they just blankly lie to me?

I don't think that they lied to you.

I had Fusion Drive issues where my system kept getting corrupted on my Late 2012 iMac that I purchased at launch. The problems started out subtly, progressively got worse over time.

The problems started less than a year after getting the iMac, which I would call Apple Support, and they would refer me to he Apple Store, which a long drive and a few tolls later, the Apple Store said the drive was fine according to their diagnostic tools. They would wipe the drive, which I would install from my back up. Everything ran fine for a while, but the problems would come back.

Then, the call to Apple Support, and then back to the Apple Store, just to have the same stuff happen again. Rinse and Repeat!

Each time I took it to the Apple Store and they would wipe the drive, the problems would come back progressively sooner.

It got to the point where I couldn't boot my iMac every few months, then weeks, and finally days.

Each time, my Fusion Drive would pass their HW Diagnostic tool.

I started getting really frustrated, as I was doing a crap load of driving, paid $16 in tolls each trip, only to have the problems come back. But, they refused to replace the drive.

12 days before my Apple Care warranty was over, the problems came back, but this time the computer wouldn't boot from anything. Not external back ups, not recovery, not internet recovery.

It was like the failing drive corrupted the boot loader.

The Apple Store had a really hard time getting their HW Diagnostic tool to boot. The "Genius" tried for two hours.

He was finally able to get it to boot, and the drive failed the test right away, so they finally fix it.


In retro spec, I wish I would have just replaced the drive myself.

I have been opening Macs for a long time, and not scared to do so, but I think in this case, it was a matter of principle, having paid for an Apple Care warranty for the first time every, having a problem with my Mac, but Apple refused to fix it.


Getting back to your issue and what the Apple Tech said:

hey told me that leaving the drive in the system and not using it is a bad idea because it can fail and then damage the system

I am thinking that this could be correct, even if the drive is unused. But, that doesn't me it would happen.

That said, if you do not want to bother opening up your iMac, I would just do some type of external solution.

You have a lot of options on the Late 2012, such as USB, TB, fast SD card, etc.

You can even run NVMe SSDs on the Late 2012 over TB. This could be the fastest single drive possible for your Late 2012 iMac, but it is kind of pricey compared to other options.

I am currently using a Samsung X5 TB3 NVMe external drive on my Late 2012 iMac. I get up to 900MBps on it.
The only way to do better than this is to get into striping RAIDs.

 

[The.Rob]

Thank you for the answers. I am still a bit confused how a drive, that is not used could damage my machine, but I'll accept that there is a possibility.

I don't really mind opening the iMac - I have done it a couple of times. I just wanted to avoid taking out the Apple SSD part of the Fusion Drive as this sits behind a lot of stuff and I remember it being a pain to get to.

But I will likely size down my 3TB Fusion Drive to 2TB and replace everything with an SSD. It's the cheapest and most straight forward approach in my mind. I don't really like booting from external drives.

 

[Juicy Box]

I saw another thread that reminded me of this one.

Someone with an iMac G3 had an issue similar to the one I described when their HDD failed, making it impossible to boot from anything, such as an external or recovery:

G3 iMac Hard Drive Failure

Just wanted to leave a record of this here as it differs from a lot of hard drive failures. Last week the HDD on my G3 iMac got a bit cranky whilst copying files - the progress bar froze for nearly a minute but then continued as normal. I didn't give it any thought but a hour or so later, the...

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