I keep all my photos on a large External Hard Drive. I store all edited psd and tiff files on this EHD as well. I also back up my LR catalog onto that same hard drive. I have a 2nd EHD where I use backup software, in my case SuperDuper for the Mac, to clone my 1st EHD to the 2nd EHD. This is done weekly, or more often if needed, so that both EHDs are in Sync with all edits made in LR or in external programs such as Photoshop or onOne. If my 1st EHD fails, the 2nd is a clone where I can easily sync all photos to the existing catalog on my computer or open with the catalog on the 2nd EHD and sync from there. I do not copy the photos to the 2nd EHD during import but rely on SuperDuper to do its job.
I back up my LR catalogs regularly, but also want to back up the photos themselves. I can do this manually but am not sure if -- in the event of hard drive failure or other disaster -- I would be able to get the catalog and the files synced again. The help files I've read talk about copying upon import, which I don't want to do, or backing up the catalog alone, but not the photos themselves.
The best backups are automatic, so it doesn't depend on a human being remembering to perform the task, and it doesn't depend on a human being having enough time to perform the task. There are many third party software solutions to do this.
If you perform a backup and maintain all of the folder structure and file names unchanged (which all bakcup software will do for you), then restoring the catalog to working order should be a ten second task. The instructions are here: Adobe Lightroom - Find moved or missing files and folders See figure 4