We've always sat at ~20/30gbs used and now we have 30/30gbs being used. We have no idea why. I can't find any documentation on how to check what would be using up that space.
Also our store and forward is empty, and everything else looks great and CPU usage is 2-4% which is normal for us.
Over the last 30 minutes its gone down after our restart from .9gb/30 to .6.
Try something like du -h / or wherever you have Ignition installed and see what's taking up the most space.
The error message is telling you that the disk is full. It may be nothing to do with Ignition (other than Ignition requires free space). You need to check with the operating system to see what's filled up the disk as Kevin suggested.
I know this isn't a joke, but 
it reads funny
