What exactly does Sushi backup?


We were using Sushi as our backup utility and unfortunately we had complete failure of our web server and so we had to use sushi to do a restore of our wss 3.0 site.
However when we did the restore all the content on the main page was not restored.
The structure was not restored as it was previously. After the restore we did realise though that some of the sites were available on the backend and I had to manually go in and change the link for others to be able to view the site and I had to do some redirection so that the tabs would show for the site. However there were some sites that were not restored at all.
Is there any reason that this may have happened?