The tempdb mdf file on one of my instances is huge (almost 3GB but still have 55GB free space left on the drive)... what are the potential impacts (performance, etc)? The drive that houses the datafiles for tempdb is seperated from the others.
I wouldn't say that was large. If your normal operation has grown the tempdb to that size, then it has grown in demand to what was needed. I'd actually be tempted to pre-size it larger than this, to say about 5GB. The only impact this will have is that if you have not changed the default size, then when you restart SQL it will be recreated at 8MB, and could potentially grow in many, many increments again to 3GB. Pre-sizing it will alleviate that overhead at times when the server is busy.