. . . "You should ensure that you have enough free space on your Mac or PC to accommodate a backup that matches the capacity of your iPhone or iPod touch (4 GB, 8 GB, 16 GB, or 32 GB) if you proceed with the this backup.If you choose to restore, all data is erased from iPhone or iPod touch, including songs, videos, contacts, photos, calendar information, and any other data." . .