If SMART says fail, then that's pretty serious (although I have a drive that says fail in this OS and fine in that, so apparently subjective. Still the drive deffo had major problems and had to be replaced).
I would immediately try to back up the drive and replace it without dithering over whether there's a problem or not. The worst outcome is that a) it fails and b) can't be recovered.
EDITED: 11 Jan 2014 01:43 by DSMITHHFX