A question about 3DS Game saves

I'm planning on buying a 3DS and I was wondering, Do the games save to the gamecart like old DS games or do they save onto the SD memory? I was wondering incase the savedata would go bad on the current 3DS cart that there would be a backup save file of the game on the SD stick. Thanks. :)

Game saves are saved to the gamecart. Streetpass stuff is saved to the system. And extra data is saved to the sd card.