[rrd-users] Re: -s does not consolidate!

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Tue Mar 26 16:55:50 MET 2002

Iain Buchanan wrote:

> I have come accross a 'feature' of rrdtool that seems to contradict itself.
> The idea of RRA's as far as I understand is to consolidate and store data,
> according to some CF.  Now, I decided that instead of making my step 1 (my
> data comes in every second), I would make it the equivalent of the amount of
> data in 1 pixel (No. samples / width of graph) to save disk space and speed
> up the graphing process.  But I noticed that all of a sudden I had lost my
> maximum and minumum information.  I have 3 CF's for min max and average.
> Because I get data so frequently (every second) and I want to graph it over
> weeks and months, the maximum and minumum values are very important,
> especially as the graphing period becomes longer.

You can have RRAs that accumulate data of multiple steps in each row.

If you enter data every second, the step size (of the RRD) should
be 1 second.  Each entry in each of the RRAs can be built from more
than one step and *will* (*should*?) consolidate the data according
to its properties.  Note that there are two places where step is
specified: --step for the entire RRD (should be 1 second) and
a number of >steps< in each RRA.

try: .... --step 1 .... RRA:MIN:0.5:700:1000 RRA:MAX:0.5:700:1000
to store data in intervals of 700 seconds per row.

This should result in the lowest of 700 updates going to the MIN
RRA and the highest of those 700 updates into the MAX RRA.

Also note that --start and --end should match n*700 at graph time.
If you don't do that and if you have other RRAs with other settings
for 'steps', it could happen that one of these other RRAs is chosen
as "best match".

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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