Lightroom Backup

So I decided today to be responsible and back up all my files to an external drive. Then I decided to back up my Lightroom Catalog. The files size that backed up is only 335,000KB and I have 4 years of pictures in there. Shouldn't the file size be bigger, or is there something else that I need to back up. I probably have 7,000 pictures in my one single lightroom catalog.

LR's backup just backs up the catalog (with the database entries for file locations, edits, etc.), not your photos. Even catalog previews are not in the backup.

For example, I have 27,000 images in my LR catalog:

Catalog size = 589,416 KB
Catalog Previews folder size = 13.4 GB
Image Directory size = 378 GB

If you want to backup all your files as well as your catalog, you can always export your catalog and check the box that will include the photos. I did this when I consolidated library's from two computers. It takes a very long time. Not very efficient way to back things up. You are better off just backing up your picture folder that contains your originals to an external or NAS.

as stated above the catalog backup only contains details of file locations, tags, image adjustments etc - not the actual image files. You need to do a separate backup of the images.