[rrd-users] Re: Traffic accounting - daily/weekly/monthly

Clay Chambers cchamb at gmail.com
Fri Jan 6 00:32:54 MET 2006

In my opinion, RRDtool is not a great tool for the accounting purposes
you described.  You may be better off writing everything to a text
file or database and running reports against them.  RRDtool does an
excellent job of being flexible, but that flexibility may not be what
you need in this case.

> Now I need to extract from this data some traffic accounting information - I
> need, for each RRD to extract a monthly total bytes transferred for each DS
> (BytesIn/BytesOut) primarily and a daily total for each DS, for accounting
> purposes (therefore these need to be actual data and not
> averages/interpolations).

There will be some interpolation unless you have extremely precise
control over your update times.  This would be really tough with
30,000 rrds.

> Surely with an RRA defined as above there is 1 PDP per CDP,
> therefore no manipulation is required on the figures - i.e. each CDP will be
> a verbatim copy of the PDP and therefore usable for accounting purposes?

Not exactly.  If my understanding is correct, RRDtool automatically
does some averaging of the datapoints.  In order to get out of your
rrd file _exactly_ what you originally put in, your updates will have
to occur exactly 300 seconds apart.  Otherwise, your datapoints that
RRDtool uses internally will be averaged.  The further your updates
are away from the 300 second mark, the more averaging takes place.

Alex has written about this effect many times in the past when
referring to getting exact values on graphs.  Go back and check out
some of his past posts to the list for further insight.


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