pt-stalk can't do "less-than" thresholds
I want to set up pt-stalk to trigger when there is too little disk space left, say, 200MB. I have had to write it as a trigger against "greater than disk-size minus 200MB" instead. Servers have different disk sizes, so this is somewhat tedious. It would be easier to set up if I could just say "less than 200MB" instead.