Reviving a late-2012 iMac

[Zeusz]

Hey folks,

I have an old late-2012 27" iMac with fusion drive, and I have noticed a sudden drop of performance a while back so I decided to stop using it and come back to it later. I have Time Machine backups and a small external drive. I don't know how but I was able to recover the iMac to mountain lion with this external drive acting as the main drive, and then through Yosemite I upgraded to Catalina. Still, running the iMac off this external drive, I remember seeing the two parts of the fusion drive under Yosemite in Disk Utility, and Disk Utility told me something about having to reset fusion drive to a previous state which would mean erasing the partitions, and I said fine because I have a backup. But now, after booting up from this external drive I can't see the internal drive at all in DU in Catalina.

If at startup, I start internet recovery (cmd-option-shift-r), I get the recovery screen of Mountain Lion and I see the option to run Disk Utility. I can see the internal drive as one unit, but can't partition, can't format. When I run Verify under First Aid, it runs properly, but Repair doesn't -- it's stuck in "Status: Checking".

What is the best way for me to know 100% percent that the internal drive is toast?
If it is, can I replace the internal fusion drive with an SSD or shall I just buy a 1TB external SSD, install Catalina and try to reset from time machine?

Thanks folks in advance.

Z

 

[mbosse]

I would try running the iMac from the external drive and install the programme DriveDX (free trial). This programme ready the health situation of your internal drives (SMART data), and should be your first indication of a hard drive failure.

Magnus

 

[rmeurant]

"can I replace the internal fusion drive with an SSD" ?

I replaced the HD in my late 2012 27" iMac with a 2Tb SSD, but note that mine was not a Fusion Drive.
The SSD has made a huge difference in speed, there are various Youtube videos detailing how to go about it, and kits with SSD are available from OWC. The main problem was replacing the screen accurately; also detaching the internal cables to remove the screen was tricky. Don't seal it up till you have rebooted and made sure the new SSD is working fine.

 

[hobla]

Several late 2012s I support had their HDs failing. Moving the OS to an external SSD avoids messing with the screen and is fast enough. By splitting the fusion drive you might be able to use just the internal SSD; 128GB is usually a bit small though…

 

[Zeusz]

I would try running the iMac from the external drive and install the programme DriveDX (free trial). This programme ready the health situation of your internal drives (SMART data), and should be your first indication of a hard drive failure.

Magnus

Oh, wow that report looks nasty indeed. My HDD is dying, the SSD is sorta OK. Thanks for this suggestion Magnus.

 

[smbu2000]

Most likely it is the HDD that is failing. SSDs are pretty reliable.
If you want to split the Fusion Drive, there are instructions here:

https://www.macworld.com/article/2015664/how-to-split-up-a-fusion-drive.html


Both of the internal drives can be replaced. The HDD can be replaced with any 3.5" SATA drive. If you add in an SSD then you will need a 2.5" -> 3.5" adapter to use mounter, they are cheap to buy. Or you can just tape it down.

The blade SSD can only be replaced with a blade SSD from that same year I believe. (iMac or Macbook Pro) or if you can find an adapter.
On my 27" 2012, I swapped out the 1TB HDD with a 500GB Crucial SSD and I swapped out the 128GB blade SSD with a 768GB blade SSD that I picked up for a good price. That is the largest size blade SSD that Apple offered for 2012 (iMacs/MBPs)

Once you cut off the adhesive and remove the display the internal HDD is very easy to access as it is right there. The blade SSD is on the other side of the logic board and you have to remove the logic board to access the blade SSD.


Just running it from an external SSD is the easiest way I think as you don't have to open up the iMac.

 

[Mackata]

Hi,
I'd like do upgrade my blade as well. Which did you exactly install (768GB SSD)

 

[eric89074]

Hi,
I'd like do upgrade my blade as well. Which did you exactly install (768GB SSD)

The 2012 iMac uses the same SSD as the 2012-2013 retina macbook. Part number is 655-1796A. There’s some 768GB SSDs on eBay for $130.