[rrd-users] Re: MAXing or AVERAGing 1 steps

[Simon Amor]

round the update time to the nearest interval and that way it won't
interpolate the value.

e.g you want to log:
0 seconds  - value 0
30 seconds - value 30
60 seconds - value 60

You might actually end up updating at 0, 32, and 61 seconds. If you put
those values in, it would alter them slightly so that you get 30 seconds
between 0 and 32, which becomes 30 * (30/32)  ===> value * (interval /
actual interval).

When you fetch the values, you should end up with 0, 28.125, and 59.016.

This is what I think happens. If I'm wrong, please let me know.

  Simon

----- Original Message -----
From: Bradley Urberg Carlson <bradley at onvoy.com>
To: <rrd-users at list.ee.ethz.ch>
Sent: Friday, July 14, 2000 11:44 PM
Subject: [rrd-users] MAXing or AVERAGing 1 steps


>
> I wanted to keep a log of exactly how many modems are in-use, with
> one-minute samples.  I thought I'd put it into and RRD to make it easy
to
> graph (instead of using gnuplot or something).  I made a simple
rrdtool
> source:
>
>  create foo.rrd --step 60 \
>  DS:modems:GAUGE:600:0:24 \
>  RRA:AVERAGE:0.5:1:3600 \
>  RRA:MAX:0.5:1:5760 \
>
> When I dump the data with "AVERAGE", ...I get:
>
>  963600900:         15.25
>  963600960:         15.43
>  963601020:         14.32
>  963601080:         15.35
>  963601140:         15.62
>
> There were probably not 15.62 modems in-use at 963601140.
> When I fetch the data with "MAX", I get:
>
>  963612780:         14.00
>  963612840:         14.00
>  963612900:         14.83
>  963612960:         15.00
>  963613020:         15.00
>  963613080:         15.00
>
> Similarly probably not 14.83 modems in-use at 963612900.
>
> I thought that the "RRA:AVERAGE:xff:1:whatever" would cause "update"
to
> store an "average" of a group of 1 samples (therefore no averaging at
> all), and the data in the log would match the "update" values exactly;
and
> similarly for MAX:xff:1:whatever .
>
> I can certainly just store the values in a log-file for such a simple
> purpose; but it would be good to know what's going on here, since we
work
> on the assumption that the AVERAGE:xff:1 RRA contains the unchanged
values
> that were stored with "update".
>
> -Bradley
>
>
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