An external hard drive is a good place to start, but it may not be a sufficient solution alone. The American Society of Media Photographers (ASMP) has a good article that details the issues, threats, and options concerning backups. They advocate the 3-2-1 rule: three copies (primary and two backups), two types of media, with one copy stored off site. While professional photographers might find the expense of online backups to be prohibitive due to the size of their professional archives, scholars and students may wish to consider a service like Dropbox. See Ryan Cordell's article over at ProfHacker for more information.
ASMP reminds us that the threats to are data are numerous:
- Device failure
- Malicious damage
- Volume and Directory glitches
- Transfer corruption
- Lightning strike/Voltage surge
- Fire or water damage
- Human error
Image: Eric Hart (Eqqman), Filed, 2009. Available from Flickr under a Creative Commons Attribution-NonCommercial 2.0 Generic license.