On the dashboard of my car is a gauge that exercises me a lot. It’s the water temperature gauge, and normally these don’t bother me; in fact I’ve never really noticed them on any previous car. But this one caught my eye and now I notice it all the time.
It has five lines on it – three of the lines are marked 40, 80 and 120 and the other two (intermediate) lines are unmarked. The first problem is that the lines aren’t evenly spaced, so while I assume the unmarked lines represent 60 and 100, I can’t be sure.
A rather fundamental failing is that there are no units. Do these numbers indicate °C, °F or % of normal temperature? I’m pretty sure that it’s the first of these, but I can’t be sure.
Lastly, the precision of the gauge is such that I can only guess at the temperature; I know it’s a bit above 80, but it could be anything between 81 and 89, or so. Thus I know my car’s water temperature is 80-something of some unit or other, presumed °C.
However, I only noticed these three problems because of one thing, which you might be able to guess from the previous paragraph. The needle is always just above the 80 line. I’ve had the car long enough to know that this is normal, but at first this concerned me; it didn’t look right. So I kept looking at the gauge, and the other issues became apparent. [Yes, I do drive quite a few motorway miles ]
For some things, speed for example, I do need to know accurately and precisely the actual value, but water temperature – all I need to know is that it’s OK. Three bands would do, Cold, Normal and Hot, perhaps colour coded, and I’d be a happy bunny. Instead of wondering why it’s just over 80, I would see it was green and normal.
The point is that this applies to monitoring computer equipment. Of course, just like my car’s speed there are some values you need to know exactly. But for the majority, all most people need to know is that it’s OK. If you can look at your enterprise management dashboard and see everything is just right (the Goldilocks zone) you can stop worrying.