This is still an ongoing issue with the latest release of FreeNAS, however this fix can be applied to resolve the issue.
I noticed that the S.M.A.R.T (Self-Monitoring, Analysis and Reporting Technology) keeps on crashing after updating from FreeNAS 11.1 Now this does not prevent FreeNAS from running but it is a useful tool in detecting and reporting various indicators of drive reliability with the intent of anticipating imminent hardware failures.
Having looked at various forum posts, it turns out that the most likely culprit causing S.M.A.R.T to crash will be the USB boot device and by disabling S.M.A.R.T on the USB you will be able to run the daemon.
To disable S.M.A.R.T of the USB boot device follow the procedure below.
While logged in to the FreeNAS server via the web GUI navigate to storage in the side menu and click on the View Disks link. You should now see the list of disks running on your server as illustrated below.
Now look for your USB boot device ( It will be the entry with the smallest disk size.
Click on the disk you want to edit (in this case it is da0 with a disk size of 30.8GB) and click on the edit button. You will now see the following screen.
Now remove the tick in the Enable S.M.A.R.T option and click on the okay button you will now be returned to the view disks list. You should now see that the Enable S.M.A.R.T has been set to false.
This should now resolve the issue.