For the Pool computers and the login computer you have a personal home directory that is shared by all these computers. The disk space is limited for each account. You can query it on the Linux pool machines and login-stud using the command

quota

Dont let your home directory fill up! - A graphical login would not be possible any more, as a log file is written. In this case you can help yourself by logging in to a text console or via ssh and deleting some files. Check quota again afterwards.