Late 2012 iMac Fusion SSD Errors - Is this right approach?

[Jenzbullets]

Long time reader, first time poster

My late 2012 27inch iMac has a 3TB Fusion Drive. I tried yesterday to upgrade to Mojave and the install failed saying my SMART Status was failing.

A quick check with DriveDx shows that the Wear count is the issue as per the attached image. The HDD portion of the Fusion drive is fine. As you can see from the hours indicator the SSD is quite old! It does however work perfectly well and I am NOT observing any issues.

Given the challenges and cost of getting it replaced I have thought about the following:

Using my spare Samsung External 500GB T5 as the boot drive via USB3. Is this sensible?

If I do this am I going to see any performance hit over the 128GB internal SSD?

And can I also still use my internal 3GB HDD portion of my Fusion Drive as a hard drive?

Kind regards Neil.

 

[Fishrrman]

"Using my spare Samsung External 500GB T5 as the boot drive via USB3. Is this sensible?"

Yes, it IS sensible.
In fact, it's A VERY GOOD IDEA (the shouting is intentional).

"If I do this am I going to see any performance hit over the 128GB internal SSD?"

There might be "a slowdown" from what benchmark apps would indicate, but I don't think you're going to notice it. Are you using the external SSD right now? If so, how does the overall performance "feel"? Good enough?

I've been booting and running my late 2012 Mac Mini for almost SIX YEARS from an external USB3 SSD. It runs as well today as it did when I took it out of the box in January 2013.

"And can I also still use my internal 3GB HDD portion of my Fusion Drive as a hard drive?"

Yes, but there could be a problem.
That's because the "fusion drive" is "melded together" via the OS. The internal SSD and HDD are "fused" to "look like one drive".
If the internal SSD fails -- goes kaputt -- your entire fusion drive will disappear.

Do you keep a backup?
If not, YOU'D BETTER START THINKING ABOUT THIS (the shouting is again intentional).

It is possible to "split" ("de-fuse") the fusion drive into "standalone" SSD and HDD. But again, you have to BACK IT UP FIRST, then do the split, then restore to the HDD.

My recommendations:
- If the fusion drive still works "without issues" (as you mentioned above), I'd just keep using it for now, BUT
- I'd also keep a CLONED BACKUP of the internal drive (created using either CarbonCopyCloner or SuperDuper).
- That way, if the internal SSD ever fails, you can plug in the clone and "keep going" as you figure out what to do next.
- If you've got the external SSD set up and running well, and like running the iMac that way, that's "option number 2". But again, keep the fusion drive backed up.
- if the internal SSD fails, I would use Disk Utility to "de-fuse" the fusion drive, set up the internal HDD as a "standalone HDD", keep my "large libraries" of data on it (to save wear and tear on the external SSD), and leave the internal SSD "dead, but in place".