Professional backups:

Daily (if the application data is crucial)
Weekly
Monthly

If daily, even days and odd days backups should be kept apart.
Backups, on whatever media (memory stick, hard disk, DVD, tape or other) are to be kept away from the computer itself, in a protected place etec. etc. etc.

Partitioning will not save your data in case of mechanical failure that will destroy the disk surface.

I don't say that you should follow all the above (we do it in my office, on weekly basis, but that's normal with a commercial activity stored on the server) BUT a backup should, in my opinion, be made in an external drive (of whatever type) and kept away.

Last but not least: a year ago my laptop was stolen. No partitioning can save you from something like this...

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