[rrd-users] Dynamic Steps

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Tue Apr 23 00:14:32 CEST 2013

> But there is also something else you are missing. Your power meter has 
> already averaged the data. Each time it ticks over a unit, then all you 
> know is that since the last tick you have used one unit - but not when you 
> used that unit within that period.


> On a domestic supply, I cannot see how you could need to deal with more 
> than one unit/second. To do so would need you to use 3600kWHr/second, 
> which is 3600kW, or 3.6MW.

No, he's getting a tick per Wh, so 1000 ticks per kWh.

3600W is high but possible (more than 15A).  No problem for RRDtool, except 
if you log maximum rates seen.

> However, RRD will correctly handle multiple updates within one step. So if 
> you did manage to reach that sort of power usage, and you had 10 minute 
> steps, then it would cope with you using 3 or 4 units in one step, and 
> will work out the right average after the data is normalised.

Average, yes. But maximum will be set to the average during the step 
duration, so it could be less than the real maximum (or am I making a 
mistake here?)

More information about the rrd-users mailing list