That will not work because when he strikes 300 GB composed the disk will be complete. The old file will still exist and finish till he eliminates it.
One method to do this is to compose code that modifies the directory site straight to eliminate the file prior to copying it. That erases the direct entry however does not touch the file obstructs. However to make sure that you do not overwrite blocks of the old file you need to understand which obstructs come from it and which do not. So you’ll need to make a list of blocks that you can compose to and after that as you check out and dispose of blocks from the old file you can get those blocks back to compose to. Then you put an entry in the directory site that indicates your blocks rather of the old ones. On the other hand you’ll need to make certain that definitely no other program operating on the system touches the disk.
Another is to plug in a 1-TB USB drive and utilize that as short-lived storage.