The function of disk-filltest is simple:

* Write files random-######## to the current directory until the disk is full
* Read the files again and verify the pseudo-random sequence written
* Any write or read error will be reported, either by the operating
  system or by checking the pseudo-random sequence
* Optionally, delete the random files after a successful run

Homepage:
https://panthema.net/2013/disk-filltest/
