Catastrophic Hard Drive Failure

Last night my Late 2012 27-inch iMac experienced a catastrophic hard drive failure. In the minutes leading up the event, I was stitching together some photos which resulted in my iMac running out of memory. I assume that the virtual memory system kicked in, as my computer immediately became slow to respond, and I could hear busier-than-normal hard drive whirring noises. After force-quitting the photo stitching application, my iMac regained normal responsiveness. Abandoning the thought of using my photo stitching application, I proceeded to check my Facebook stream on Safari. A few minutes later, I heard loud “scratching” noises coming from my hard drive, so I quit Safari and attempted to reboot. Unfortunately the iMac refused to reboot, shut down, or obey any other commands. I had no choice but to force a shutdown by pressing and holding the power button. I waited a minute and restarted my iMac. I heard one more loud scratching noise from the hard drive, and then the machine went silent.

Fortunately I have a portable external hard drive where I’ve installed macOS High Sierra (version 10.13).

By pressing the “option” key during startup, I was able to select my external hard drive as the boot volume and successfully launch Finder. I was immediately shown the following message:

I assumed that this was in reference to my internal hard drive. Not a good sign. At this point, I ran Disk Utility to try to repair the volume so that I could mount the internal hard drive and access its files. Here’s what I saw:

Another bad sign. Disk Utility said that my internal hard drive (ST3000DM001 Media) was “Uninitialized” and that its capacity was 4.14 GB when in reality it is a 3 TB fusion drive (note the SSD portion as indicated by “APFS Physical Store”). First Aid failed to repair either the hard drive or the SSD.

Next I launched TechTool Pro and ran a suite of diagnostics. The hardware tests passed for the most part, until it got to the Surface Scan where every single block was designated a bad block.

My original plan was to mount the volume, perform a 1-pass secure erase, and install a fresh new operating system. However, given that I cannot mount my internal hard drive, I have decided to format one of my spare external hard drives, install a fresh new operating system on it, and run the iMac from the external drive for the time being.

I realize that I could replace the internal hard drive, and while it appears to be rather affordable if you buy the parts and install it yourself, I have a fusion drive so I wasn’t sure if I should attempt the replacement on my own. I asked Google but didn’t find any articles about how to replace a fusion drive with a regular hard drive. I suspect that it is possible, but I would not be surprised if the procedure was slightly different. Also, I prefer not to purchase another Intel Mac just as Apple begins its transition to its own Silicon processors. So meanwhile, assuming nothing unexpected happens, I’ll be using a temporary external hard drive for my iMac boot volume, in hopes that this makeshift configuration will buy me enough time to get a new Silicon iMac.