I am on Mountain Lion 10.8.4 nd cpu is Mac Mini. Since yesterday I am unable to find one of the volume, which is 120 gb in size. I don’t know what happened but this volume is not showing up in finder. I have very important daily usage files in the volume which are now invisible to me. This is strange as never ever such thing happened before on my mini. Is my hdd faulty, I need to get back some file urgently. Please help me as I don’t know what to do.