I am a strong advocate of the 3-2-1 Rule of Backups, which is: At least three (3) backup copies total, in at least two (2) different formats (hard drive, optical media, thumb drive, etc.) with at least one (1) backup being stored off-premises, whatever that means for your specific situation (cloud storage/remote repo, at work/home/school, safety deposit box, etc.)
3-2-1 Rule of Backups
As far as I am concerned, if it is not backed up 3-2-1 it might as well not exist at all, because when it's gone, it's gone.
The at least's in that formula strongly encourages doing more than the minimum, especially in whatever area(s) you feel might be the greatest risk, whether that be location, form, or just sheer number of copies, or all of the above.
Just make sure you develop a naming/version numbering system that allows you to quickly identify the latest copy of the resource, so you may be sure your backups are the latest versions (along with normal version control operations, in order to be able to restore some prior versions as needed as well.)
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