It depends entirely on how you write the software, and also (obviously) on the resolution you want to use.
As I said, the only way to detect the resonance is to sweep past it - only once you're past the peak (and it's going back down) do you know you've found the resonant frequency. You don't need to log all the readings, just the last 'so many' in a circular buffer, so once you've detected you're past the peak the stored values will include the resonant point.