SMART reporting on SSD drives in Catalina

Last week I upgraded my iMac to Catalina, and immediately received a SMART failure alert from TechTool Protection, saying that the SSD component of the iMac’s Fusion drive was failing.

Before this, I’m pretty sure that the SSD drives were not being reported at all, i.e. they were not supported. But, I don’t recall seeing anywhere that Catalina included a change to now support SSD drives.

My suspicion was that it was a false report. Maybe a software incompatibility: my iMac is from 2017, and TechTool Pro is also an obsolete version (11.0.5).

And then, after I re-cloned to an SSD external drive and encrypted it, it too was reported as failing SMART! I find it hard to believe that both drives suddenly are simultaneously are failing.

What I’m wondering is, is it macOS that is now returning the SMART data from the SSDs? That is, did something change Catalina? If it isn’t macOS, then is there a way to find the driver responsible?

I did have a SoftRAID beta installed at one point but I removed it long ago, hopefully completely.

Right now Disk Utility says the external SSD’s SMART status is Verified, and the Fusion drive is failing, but Disk Utility doesn’t separate the Fusion HDD from the SDD. Disk Warrior’s smart reporting says that only the HDD is supported and is fine.

Now this is more important because it is blocking the Big Sur upgrade.

And here’s something weirder: System Information says the individual components of the Fusion drive are both SMART Verified!

NVMExpress > Apple SSD Controller > APPLE SSD SM0128L > S.M.A.R.T. status: Verified
SATA/SATS Express > Intel 10 Series Chipset > APPLE HDD ST3000DM001 > S.M.A.R.T. status: Verified

Why are the components OK but the Fusion drive is “failing”?