SSD Keeps corrupting and requires re-formatting

It's a late 2011 iMac with an SSD installed per instructions and kit from iFixit - with the exception of requiring a different cable to the one provided. The Drive is a Samsung 850 EVO 120GB

It worked fine for about 18month as a fusion drive, then it and the hdd started corrupting. So I split the drive and replaced the HDD (6yr old drive). Decided that I'd avoid the Fusion approach and kept the SSD as the boot disk and the HDD as the User disk (good decision it turns out).

But, every 2 weeks or so the SSD is faulting to the point that it requires formatting. Diskutils gets the dreaded "exit code 8" and even FSCK cannot fix it. I've updated to High Sierra in the hopes it the APFS would help, but so far no joy.

So after thoughts on the following or something else I've not considered:

  • Could it be a cable that has come loose? (thinking if I have to open it up to swap the SSD and CD ports as the CD is in the 6gb/s port by default for some reason
  • Could the cable be faulty now (was from ebay as it was the only place that had it)
  • Is it the drive failing somehow? oddly I can disk util check the root of the disk fine, but the container for the partition fails. Drive is less that 3 years old
  • A temperature issue? It's installed under the CD drive as instructed and I'm now using Mac Fans Control to monitor the SSD temperature rather than the CD drive
  • Could there somehow be a remnant of the old fusion setup still on it? I ask this last question because even Single User mode failed and strangely one of the errors mentioned in the boot error for it was showing efi_fusion_pairing:637 fusion uuid: xxx

Side note, when I split the drive, I followed the instructions here:

And then did a format via command line to reset the drive.

Last thing, when the fusion drive originally failed, I managed to repair it a few times using FSCK in single user mode but then that stopped working too.

Would love to know people's thoughts. I'm technical and have read a lot about it and run every check I can find on through the terminal

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What is your OS version?

Are you cloning your drives or restoring from a TimeMachine backup? Why I ask is something is coming back which is messing you up here with your last point of getting the 'efi_fusion_pairing' error

I have a 2011 with a Samsung 500 EVO drive which is not having any problems in the same config which was running El Capitan upgraded to Sierra and now running High Sierra. So it could be either a cable issue or software or even both!


Hey Dan,

Thanks for replying. I mentioned it was High Sierra as I was hoping the APFS would help. And all upgraded to the latest non-beta version.

And Originally I did restore it from time machine, but last 2 I did a clean install with all new account. And have not reinstalled any old apps from Time Machine. And User accounts left on the old HDD bar one new account I create during the new setup as a 'local' super account if you will which lives on the SSD.

I did run Etre over it to to ensure that I'd gotten all the old extensions that have hung on over time. Amazing how much legacy stuff hangs on.

Also realised that the old solid HDD was 'blessed' so have unblessed it now.

I'm leaning on trying a new cable as a quick easy fix. That way ticks that box and the loose cable. Just not keen to go all the way back into the motherboard again :)

Wonder if there's something in one of the old User accounts, but even Etre hasn't found it if there is.


hi Greg, I wonder if you have been able to check how much GB have been written to the SSD to this date? could it have exceeded its limit?


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