I have decided to store my photos for back-up. I am struggling with file type. Should I store the RAW file that comes from camera or DNG file where all my editing has been stored.
You can save DNG if you want, but you can also save RAW+XMP. (which would take significantly less space than RAW+DNG)
To export your Lightroom adjustments to an XMP sidecar file, either automatically or manually on demand, see here:
1.Choose Edit > Catalog Settings (Windows) or Lightroom > Catalog Settings (Mac OS).
2.Click the Metadata tab, and then do either of the following:
◾ To write adjustments and settings metadata to XMP, select Automatically Write Changes Into XMP.
◾ To write adjustments and settings metadata only to the catalog, deselect Automatically Write Changes Into XMP.
If you don’t write adjustments and settings metadata to XMP automatically, you can select a file and choose Metadata > Save Metadata To File.
Another thing you should back up regularly is your Lightroom catalog, since that contains more than only the adjustments on the images (tags, histories mainly)