See Make a split library portable and organize your library completely on your other drive, or at the very least upgrade the layout so that Mobile Applications is moved to inside the media folder. (Rearrange files, consolidate, remove originals to reclaim space.)
This technique can be used to move the iOS backup data as well.
Relocate iOS device backups
- Make a new folder called MobileSync at the root of the drive you want the backup data to live on, e.g. as D:\MobileSync
- Use Windows Explorer to move current Backup folder at <SystemDrive>\Users\<User>\AppData\Roaming\Apple Computer\MobileSync\Backup into the folder you just made. If the backup folder is large this may take some time.
- To make iTunes look for the data in the new location copy the text below, open a command prompt, right-click to paste in the command, edit the drive letter/path if needed, and then press <Enter>.
MkLink /J "%AppData%\Apple Computer\MobileSync\Backup" "D:\MobileSync\Backup"
If you want the backup elsewhere replace D:\MobileSync accordingly.
Note that while this method works for iOS device backups it cannot be used to redirect sections of the media library.
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