Hello.<br><br>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 wrong...<br><br>To cut a very long story short, I am now of the opinion that I should not set up my RRD store as <br>
DS:$sensor:GAUGE:300:-50:100<br> 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.<br><br>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).<br>
<br>Therefore, I'm looking at redoing the whole lot from scratch. Questions so far:<br><br>DS:delta:DERIVE:300:U:U<br>appears to support only integer values. Is this a bug, or a design feature?<br><br>Since I have a number of sensors, and wish to evaluate the pseudo-equations<br>
delta=mean(inside) - mean(outside)<br>and<br> the differential rate of change of temperature<br>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.<br>
<br>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...<br>
<br>Best regards,<br><br>Phil<br><br>