Yeah, the difference with the disk full alert and the alarm is that the alarm is emitting a very obnoxious noise continuously while you're trying to debug it; and in the meantime, not actually providing a useful service, like the server is. Trying to debug a problem at 3 AM when you just want to go back to sleep because there isn't anything actually wrong, just faulty alarm hardware, is not nearly so useful as clearing out some space on a full disk when it is in active operation.