Late 2012 27" iMac Dead Fusion Drive?

[iEdd]

Hi all,

I have a late 2012 model iMac with a 1 TB fusion drive that was making some weird buzzing noises a few months ago, which I don't think were just fan noises. I ran some TechTool Pro tests at the time and got some bad block warnings about the hard drive, but life got in the way, so I just left it (while continuing to back it up).

Since then, the noises have stopped, but two days ago, my iMac died in the middle of doing a SuperDuper backup. I can still reboot it and do some things, like open Safari and other recent apps, but if I go to explore files in the Finder, it will hang and beach ball in certain folders, and either stay that way forever, or the iMac will crash entirely/restart.

This leads me to think it's the mechanical HDD part of the fusion drive, and the SSD part is fine (booting works and recent apps sort of work). I also tried running EtreCheck, but it hung and beachballed on "checking hardware", and I had to force shutdown.

Is there any definitive test I could use (or better yet, a bootable utility I can put on a flash drive) to determine if it is the fusion drive, before I delve into cutting my computer open?

Thanks.

 

[tiktok]

You are not mistaken I fear. I had the same, I was able to boot my OS (DIY fusion drive with a 512GB Samsung EVO) but when I was accessing data that was located on the HDD it hung or crashed.
Not sure, but maybe if you run diagnostics? ( Press D while booting ) - I've never done this so I don't know how deep the tests will go there

 

[iEdd]

Thanks for your reply, tiktok.

Since posting, I've been able to run other tests, including EtreCheck (all passed), and TechTool Pro 5 (all passed, including HDD and RAM). However, bits of the UI still disappear – desktop icons vanish, desktop itself turns black, and unpredictable beachballing/crashing behaviour happens when exploring files deep in the Finder.

Bit annoying that there's no consistent test failure. I'll try booting off an external drive and seeing if I get any weird behaviour; if so, I can run on one RAM stick at a time to isolate any memory problems. Just gotta be completely sure it's the fusion drive before I go splitting this thing open by its screen.