This post will tell you how to backup iPhone to external hard drive, such as USB flash drive on Windows and Mac. In order to release the disk space the backup files occupy, you can backup iPhone to external hard drive instead. Usually while you back up iPhone through iTunes on Windows or Mac, the backup file will be automatically saved in default location on the limited disk space.
Before you do that, make sure that the new library has all the contents of the old one, so you don’t accidentally delete something you want.How to Backup iPhone to External Hard Drive on Windows and Mac
Time Required: Depends on the size of your iTunes library Restoring your iTunes library from backup will let you overcome a data loss or make moving the library much easier. If you had the good sense and foresight to backup your iTunes library on an external hard drive, life is good for you if you have a hard drive failure or need to transfer your iTunes library to a new computer.