I've been storing my sizable iTunes Library on a JetDrive SD card since my Macbook Pro 13 just doesn't have enough space on the SSD for my Library and all of my other files. However, I've had consistent performance issues with iTunes since updating to 12.0 and onwards. Crash on launch and other critical issues. I can't tell if it's the bloated software or my external storage that's causing this. Is it one or the other or both? I honestly don't know anymore.