not petty at all. I think this is important stuff - we as employees are viewed more and more as commodity, and as such, have to be aware of what we are worth. It's not like you'd ever see a gas station selling gas at lower than market value.

Not sure what to think of your mentor's advice. The bit about not negotiating during hiring is weird, but maybe he knew that they were fixed on the salary they could offer and planned to turn away anyone who asked for more. FWIW, I've kind of come to believe the whole "mentor" thing, at least in tech, is hogwash. I think it's usually a lightly veiled vehicle for nepotism.. but then again, I am kind of jaded. haha.

I think were I in your shoes and had the energy to do so, I would throw some resumes out for potential back up plans, and then ask your boss if the upcoming raise is going to be at least [whatever you feel you're worth]. then if they say no, you can be ready to move on. That's all assuming that the pay is a deal breaker for you.. it's tough to decide on these things.