Dyson

In Linux, /dev/full or the always full device is a special file that always returns the error code ENOSPC (meaning "No space left on device") on writing, and provides an infinite number of null characters to any process that reads from it (similar to /dev/zero). This device is usually used when testing the behaviour of a program when it encounters a "disk full" error.

http://en.wikipedia.org/wiki//dev/full