Fedora upgrade recovery procedures?

I have an older Toshiba laptop running FC16. I also have a DVD with an install .iso for FC17. I booted off the DVD, it noticed the existing installation and offered to do an upgrade. About 5 minutes into the upgrade process it had arrived at the point where it was about to install the ~4000 packages. At that point it produced a message saying there was insufficient disk space on /usr (short 2MB, this on a 12G logical volume, with considerable space available on the physical volume) and the install would exit. Trying to reboot afterwards produces: sh: cannot set terminal process group (-1): inappropriate ioctl for device sh: no job control in this shell and drops into a dracut shell. Running the "rescue" operation on the DVD says it can't see any valid Linux partitions. Nevertheless, there are other OSes on the disk and booting into them suggests the Fedora LVM is intact (as well as the Fedora boot partition, etc.), although /usr is *empty*. So am I out of luck here, or is there some kind of recovery possible? Maybe a Live-CD to do some amount of file tweaking? Does an upgrade provide any recovery features at all? Is this the right mailing list to post this question? Thanks for any thoughts.