[rrd-users] Temperature Monitoring

Phil White manx.biz at googlemail.com
Wed Feb 15 23:24:00 CET 2012


After a couple of years using RRD to store my temperature sensor logs, I
lay in bed the other day and cursed, after deciding that I was doing it all

To cut a very long story short, I am now of the opinion that I should not
set up my RRD store as
 simply because this is not the information that I am *really* interested
in - it is just the way that most people do it, because that is the way we
are used to thinking.

I'll try to explain a bit better. I have several sensors - some inside the
house, some outside. When I started, the aim was to monitor the
temperature, and use this to automate heating. But, rather than the
*actual* temperature, I am actually more interested in the *relative*
temperature difference between the average outside temperature, and inside
- together with the rate of change in temperature (which are probably
related in some way).

Therefore, I'm looking at redoing the whole lot from scratch. Questions so

appears to support only integer values. Is this a bug, or a design feature?

Since I have a number of sensors, and wish to evaluate the pseudo-equations
  delta=mean(inside) - mean(outside)
  the differential rate of change of temperature
does anyone have any opinions / advice on the best way to store the data,
and how to calculate this? I have had a few attempts, but am getting
nowhere fast on these.

I have been using one RRD file per sensor - but I do not necessarily have
to do it this way (though it is easier at the moment). I am looking at
efficiency of CPU and disk I/O, as well as ease of gaining access to the
computed values I need. I could continue recording temp, and then
evaluating the required figures each time - but it seems sort of wrong...

Best regards,

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