How to change the iTunes U folder on Mac

Purpose of this folder:

When iTunes synchronizes photos to your iPod, it actually converts and resizes them into 16-bit bitmaps in resolutions appropriate for the iPod. It stores the converted photos in the iPod Photo Cache folder before transferring them to the iPod. This basically allows iTunes to quickly add/remove photos from your iPod without having to reconvert them every time. If you remove a photo album/folder from your iPod (by unchecking the box in iTunes preferences), it will still leave the pictures in the cache in case you want to add them again in the future.

Possible workaround:

Move the iPod Photo Cache folder to the location of your choice, and make an alias (shortcut) to the folder in its new location. Place the alias in the folder where the iPod Photo Cache originally was (usually in the Pictures folder) and make sure the alias is named "iPod Photo Cache". When iTunes looks for the iPod Photo Cache folder in the Pictures folder, it will instead find the alias, directing it to the new location.

You didn't specify the OS of the computer but on Windows that would be a junction point.

It depends on your iTunes preferences.

1.If iTunes is running default, iTunes actually copied all that media to your local drive, and you would have to delete it manually via sorting by "Date Added" to remove it.

2.If you have iTunes set to reference the files, when you disconnect the drive iTunes has some pretty annoying behavior where it will try to maintain the link but it will become a ghost music icon, the best way to get rid of these is sort by "Date Added" in your library and remove them manually.

These behaviors can be checked under iTunes preferences, I copied this pic from the Apple support site under HT1751: