I have the 256gbssd MacBook retina pro. Im a graduate student so didn't have the $$ to spend on the extra hd space. I don't do any photo editing or sound editing. I was thinking of buying a 128gb sdcard and just leavin my photos and iTunes library on it. Both of them together are at about 90-100gb. My question is has anyone done this? Is 45mb/s transfer rate of the sdcard good enough to store the music library on the card and not have problems while iTunes accesses the library to play music etc..?