It is interesting that many of us are having this same message come up while trying to install Yosemite. A message I have NEVER seen before on any of my Macs.
In my case I am loading a Mac Mini Server with two hard drives (not being used as a server). The main Drive, where I want to load Yosemite, is getting the SMART message, whereas the secondary drive is being described to me as the backup drive for Time Machine (which it is not - I use an external drive for that).
If Yosemite is incorrect about my second drive, what assurances do I have that it is correct about the first one.
So, while Tim says I should trust that the message regarding the pending failure, my confidence in Yosemite is being tested.
QUESTION... is there any other software we can download to verify the SMART error message?