[rrd-users] counting pellets with rrd

Matthias Lemke m at box.li
Sat Dec 10 22:35:04 CET 2011

Simon Hobson schrieb:
> Matthias Lemke wrote:
>> I connected my eta pellets heating unit via webservices to my home
>> server. I am interesting in counting the amount of pellets per day (warm
>> weather days should have low counts of pellets). The unit has a counter
>> that counts from zero up forever... The unit sends the value in "kg".
>> normally I have around 15...20 kg / day.
>> I want to have a graph that shows me the kg/day. So I thought that I can
>> write one data per day to the rrd. But, after two nights of testing and
>> testing, I have no idea for the correct rrd setup...
>> Do You have any hints for that challenge :) ?
>> I want to have two RRAs:
>> one vor 400 days, one data per day (kg/day).
>> second one for kw/weeks for 500 weeks...
> Firstly, remember that RRD stores <things> per second. No matter what 
> you feed it, that's what it stores.

I remember that from my network usecases (bytes/second)... ok.

> So lets say you feed it a value once per day, and the value is 15kg - 
> then rrd will convert that to 15/86400 = 1.736e-4 (or 0.0001736) 
> kg/s. Your options are really to multiply by 86400 before storing the 
> value, or on extracting the data.

what do You mean with "extracting the data"?

multipliing was one of the idea.... right.

> Another issue is that rrd works in UTC, so the "days" it will work 
> with are not the same as your local days. You just need to be aware 
> of that.

good point, thanks.

> You will want a counter data type since you conveniently have a 
> counter to feed it with.


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