How to Change the Location of Your iTunes iPhone Backups (Mac)
These are instructions on how to change the location that iTunes uses to backup your iPhone, iPad, or iPod touch for Mac.
Launch Terminal from your Applications:Utilities folder.
Navigate to the MobileSync directory by inputting the following command and pressing Return.
cd ~/Library/Application Support/MobileSync
Rename your old backup folder using the following command.
mv Backup Backup_Old
If you haven't created a new folder to store your backups please do so now. You can do this with Terminal or Finder, or you can use an existing folder.
Example: mkdir /Volumes/Storage/iTunes/MobileSync/Backup
Input the following command to create a symbolic link to your new folder.
ln -s /Volumes/Storage/iTunes/MobileSync/Backup ~/Library/Application Support/MobileSync
You can use Finder to verify the symbolic link was created. Notice the arrow at the bottom left of the icon.
Test out the change by performing a backup with iTunes and verifying that your files are backed up to the new folder.