[rrd-users] rate per day graph from rate per hour DS

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Jan 30 12:19:41 CET 2007

On Tue, Jan 30, 2007 at 01:07:30AM -0500, Ben Griffith wrote:

> >This will of course be countered by the opposite: your boiler switched
> >on a fraction of a second ago and you note "1" where the real status
> >should have been "0".
> I thought of that, but I figured in the end the two cases would cancel each
> other out.

Yes, that's what I tried to say. Sorry, not native English.

> I could try updating more frequently.  I think I'd have to
> adjust the rate multiplier accordingly.  So if I update every 15 seconds I'd
> have to multiply by 900 (number of seconds in an hour divided by the number
> of 15 second blocks in a minute) instead of 3600 to get the number of
> minutes the boiler was on in an hour.

If you feel a minute to be close enough, by all means keep it this way.

You are currently updating with "1" for an entire hour on, "0" for an
entire hour off, and anything inbetween for a mix.

If the boiler is on at the start of a new hour, stays on for another
15 minutes, switches off and stays off during the rest of the hour, I
expect a number around 0.25/3600 in your database.  Is this correct ?

When you look at your data (dump it, or fetch from it) you should see
numbers between 0 and 1/3600 (0.0 .. 2.7777778E-04).

>> Your step size is 3600 seconds.  Each minute you add another portion
> >of the hourly statistics, I think using an averaging computation.
> >(not 100% sure, but pretty sure)
> Doesn't it just add up all the entries to get a total for the hour, then
> from that a rate per second?  Or does it actually compute the rate
> throughout the hour, on the fly?

I'm not sure what it does for "absolute".  For "counter" it saves
the value multiplied by time, and at the end (when the PDP is moved
into an RRA) dividing by total time results in a rate.

This rate is not available to you.  Only when a PDP is shifted to one
of your RRAs, it becomes a CDP.  You can only graph CDPs.

Try, in parallel with your current setup, to update another RRD using
GAUGE.  You should end up with numbers like 0.25 (not divided by 3600)
which mean the boiler was on during a quarter of the interval (whatever

Alex van den Bogaerdt

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