Got on site one morning to find a SCO box pretty well jammed solid.
Some job had gone wrong overnight and was still trying to write a humungous log file. The box had been set up without partitioning the storage much if at all so the file was in the root partition along with more or less everything else.
Simply deleting the file wouldn't work because the program was still running; until it closed its handle on the file the disk space wouldn't be released. Deleting any files that could be spared didn't help much because the space released would be filled by the elephant in the room almost immediately.
It turned out that a SCO box with a full file system ran very v.e.r.y v..e..r..y slowly, probably because the file was buffering a load of stuff and choking most of the memory so everything else was trying to run in about 4K left over and thrashing. That made running ps to find the PID to kill more or less impossible.
And the box was a couple of hundred miles away at the end of a slow modem link - not that the speed of the line had much influence.
Eventually it got arm-wrestled into submission. I like to install Unix systems with multiple partitions, especially keeping directories that might grow, such as /usr/spool or /var separate.