Parts of the following section might sound overcautious, but the points we make are based on real-world experience. In Backup, we suggested that you save at least three copies of each of your images:
On your everyday hard disk for quick access and further processing
On an external, portable medium, such as a hard disk, DVD, or Blu-ray disc
On an additional, offsite medium
Peter Krogh’s book  contains a detailed discussion on the subject of data security.
Great images (especially if used professionally) are worth a lot of money, but serious amateur photographers, too, should take the time and the trouble to ensure that their files are stored securely. Increasingly cheap and easy-to-use storage media leave you with no excuse for not ...