No1 liked Sony's idea creating a ps3 with flash memory (12gb) You can use and external hard drive but it will cost u money so...
I recommend u too use the cheapest bracket which is the 40gb i think . It's good for storing game file directories but not meant for huge games but still worth it .Dont worry if u have a low hdd on ur ps3. Other method is: Instead of bracket, u can use an 2.5 inch SATA drive, mostly found on pc or laptops,they vary accrording to their RPM. 5400 rpm is enough for ps3. For further help, use youtube