Don’t let it be a disaster. Short and sweet, from iLibrarian:
What Happens if Your Library Systems Go Down?
For full-fledged disasters (floods, fire, earthquakes, hurricanes, shooters, bomb threats, bombs, building collapse, etc.) check with your managers, your organization, and your local librarian community for specific and recommended disaster planning checklists. (And if they don’t help, use The Google! Don’t let others’ failure to prepare become your disaster.)