Super cool trick to see what process is holding up disk space for a file handle for a file that's already been deleted.
This is wonderful.
An example would be seeing disk utilization at 80% and you clean out all the disk space and the utilization is still at 80%.
This happens when a process is holding a file handle open for a file who's content has been removed.
Here's how you find the PID of the process holding open file handles for deleted files:
lsof | grep deleted