Restricting Hard Drive Space Usage

Does anyone know if there is a way to restrict the amount of space avaliable to users on a hard drive?

Here's an example. We have users who like to fill up our server with files. I would like to put a hard limit of say if there is 200 gigabytes free it will stop allowing anyone to write to the system. At this point we could then contact the users and tell them to start cleaning the drive and we could then set the limit to 100 gigabytes to give them some breathing room while we continue to clean up the drive.

Another thing that would be of use is there a way to have an email sent when we hit a space limit?

Everything I've found so far is restricting via user quotas but I want the space limit to be disk centric and not user centric.