PokerTracker

Will I get the same performance if my main drive is a 120 gb ssd drive and my secondary drive is a 240 gb ssd drive dedicated solely to poker or is it best to keep all my poker stuff on my main drive with windows?

If there is a perfromance hit, how big is it?

You will get the best performance by having only your database on a drive on its own - that way data retrieval is not interrupted by the system accessing the disk for anything else.