I've always said that there are two kinds of photographers; those who back up their files and those who eventually wish they had. Our photographs are priceless and irreplaceable and we should treat them that way. I've seen systems that range from nonexistent to insanely complex. Here's my backup workflow:
Here's how it works
In the field, as soon as possible I copy my files to my notebook computer and also to an external hard drive at the same time. Lightroom can do this simultaneously. I leave the files on the card also, which gives me three copies of the files.
Once back in the office, I copy the files to my desktop computer, which automatically back up to another hard drive hourly. The memory cards can now be erased and put back in my camera bag. I leave the files on my notebook and field external drive for now if possible.
As I work on the files, they are continuously being backed up to a second drive and once a week to a third hard drive.
One problem remains. If some kind of catastrophe happens at the office, my computer and all my backups are in the same building. The same condition that destroys my computer would also most likely destroy my backups as well. This is where off-site backups come in. Even though it's slow, my desktop is being continuously backed up online to an offsite server. I use Carbonite. Also, once a project is finished, I make a 300 year archival DVD and keep it in an off-site location. I use MAM-A gold archival disks for this.
Nothing is foolproof, but in 25 years I have never lost a file. I'm confident that as long as I follow my system I'll be fine. What's your system? Share your ideas in the comments below!