And here is a more in-depth look at the issues..
Another thing is really large courses tend to have a number of videos associated with them. Videos are notorious for taking up a lot of compression time, and space, for actually very little gain. Perhaps it would be better to use an off-site repository for them, like YouTube. All that needs be done is to add a link and the link gets backed up not the video. Reduces the size of the backup and the time of the operation. Using an external repository can reduce your backup issues but may increase your page load times - swings and roundabouts actually particularly for external images.