Moderator Notice
@mdmorrissey - I moved your post to its own thread.
The thread you posted in was about 'recovering' calibre from a dead computer. Your question is about backup.
We'd prefer you create a new thread rather than posting in an existing thread - especially if its not exactly the same issue.
See
How do I backup calibre?
I believe some OSX users use its Time Machine feature to maintain a backup of their calibre libraries.
BR