Problem: Our student login script copies the student directory to another location and copies in a fresh student directory every time you log into the student account. This provides a consistent student experience from day to day. The problem is that the folder (called savedHomeDirs) that collects all those old student directories fills up over time and will eventually use up all the available space on the drive. When that happens the computer has no room to write temp files or cache and cannot process routine tasks.
Solution: Find Jeff and have him empty the savedHomeDirs folder because it takes an admin password to do so. I’m trying to automate the process but I haven’t worked out the details yet.
In an extreme situation where the computer’s hard drive is completely full, the machine will not boot. It will get stuck part way through the process. This happened today in studio 2. I had to boot in single-user-mode by holding down command-s during the boot process. That way I was able to clean up the hard drive with a few unix commands and free up the needed space for the computer to boot properly.
Jeff Seitz's Blog 
This problem may also be to blame with reports of DP working very slowly for some of you, on some workstations. A nearly full disk takes more time to read and write files, as the files are necessarily fragmented all over the disk. If DP seems to be running inexplicably slow, and rebooting* doesn’t help, find Jeff to clear files.
*rebooting actually makes the problem worse, as it will create another backup on the drive.