Is your media on an external drive? Best practice is to keep the media on an external drive -
from the FCP manual:
You should make a back up clones of both your media storage disk(s) and your mac system disk. Good quality, high capacity external drives are cheap. Finding and re-ingesting all your source footage is time consuming and frustrating.
There are several ways to do this, I like Carbon Copy Cloner to do it.
This will make a clone of your drive - an identical, bit for bit copy - so that if your working drive fails (which it will) you can either switch to your cloned copy and keep going, or use the cloned copy as a source and make a new system or media drive.
Cloning via Carbon Copy Cloner is fast, once you do it the first time. In subsequent cloning, the software is smart enough to know only the changes you have made and will make those same changes on the back up disk, leaving unchanged files alone.
Because I make a living off editing, I make two clones of each disk. That gives me greater security that I'll have a working back up should something happen.
In addition to the end of workday clone, I also run a clone if I am stopped for a meeting, telephone call, or lunch if time allows.
This may seem a little over the top, but if you've ever had a drive fail mid-session, you'll understand the reasoning
If you are working with mission critical, non-replaceable footage, or are on extremely tight deadlines, you should also keep a cloned drive set off property in a secure location in case of catastrophe.
Another great tool which I also use is Digital Rebellion's Pro Versioner:
http://www.digitalrebellion.com/proversioner/
which will back up my project file (not the media) and store that backup at locations, including cloud locations such as dropbox, automatically. This is great not only for backing up but it also lets me keep multiple versions - so if I mistakenly delete a sequence, for example, I can go retrieve an earlier version of the project that still has the sequence in it.
MtD