[rrd-users] newbie question

[Steve Shipway]

> "A few archive areas are also defined. The first stores the
> temperatures supplied for 100 hours (1'200 * 300 seconds = 100
> hours)."
> 
> I am wondering; is this sentence missing the word "average" between
> "the" and "temperatures"?
> 
>  rrdtool create temperature.rrd --step 300 \
>   DS:temp:GAUGE:600:-273:5000 \
>   RRA:AVERAGE:0.5:1:1200 \
>   RRA:MIN:0.5:12:2400 \
>   RRA:MAX:0.5:12:2400 \
>   RRA:AVERAGE:0.5:12:2400

No, the manual is correct.

This is because the step of the RRD is 300 seconds (5min), which is how often the data comes in.

The first RRA is: "RRA:AVERAGE:0.5:1:1200" which means 1200 rows, each holding the average of 1 sample(s).

Since the average of a single value is the value itself, this first RRA stores the received values (after time normalisation!) and keeps 1200 of them.  1200 x 300s (the step size) is 100 hours.

Then next 3 RRAs store the min, max and average for a set of 12 samples, IE over the period of 1 hour (and keeps 2400 rows, IE 100 days).

Steve


Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz
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