It’s a good idea to routinely back up, or archive, your iPhoto library in case image files become corrupted or are unintentionally erased from your hard disk.
There are two ways to back up all or part of your photo library:
Save photos to an external hard drive: If you have an external hard drive set up, you can use Time Machine or the Backup utility to make a backup copy of your photos.
Using Time Machine, an application included with OS X, is the easiest and most efficient way to back up your computer, including your entire photo library. After you set it up, Time Machine automatically backs up your computer regularly, without any more effort on your part.
Important: Time Machine can’t do a full backup of your iPhoto library when iPhoto is open. To ensure that Time Machine does a complete backup of your library, quit iPhoto periodically before backing up.
To restore photos, quit iPhoto, open the folder containing your iPhoto library, and then open Time Machine.
To open Time Machine, click its icon in the Dock, or click the Time Machine icon in the menu bar and choose Enter Time Machine.
For more information on Time Machine or Backup, see the topics in Help Center.
Burn photos to CD or DVD: For instructions, see Create your own photo CDs and DVDs.