[rrd-users] generating charts from multiples RRA

[Alceu R. de Freitas Jr.]

Hello there,
I'm a little lost here and I'm not use what I missing in the documentation to solve it.
I created a RRDTool database with the following command:
rrdtool create sample.rrd --step 3600 DS:sample:GAUGE:5400:U:U RRA:AVERAGE:0.5:4:28 RRA:AVERAGE:0.5:24:90 RRA:MAX:0.5:24:90
The database is being populated as expected, the problem is to generate a chart.
If want to generate a chart from the first RRA (a week interval, with the average calculated with 4 to 4 hours interval), that seems to be simple, I just need to specify the start and end of the week with the corresponding "--start" and "--end" command line options, for instance:
rrdtool graph "$HOME/week.png" "DEF:thisweek=$HOME/sample.rrd:sample:AVERAGE:step=4" "LINE1:thisweek#0000FF:rows average" --imgformat PNG --end 1440000000 --start 1439611200 --title='Backlog of Workflow Policies' --vertical-label 'Number of rows' --width 800 --height 600
That seems to be simple, but how do I specify to use the last two RRAa, which have an average and max (respective) for a whole day items checked? Ignoring the consolidation function (AVERAGE or MAX) specified in the graph command, how do I make sure I'm fetching from the correct RRA? Only by using "--start" or "--end", or do I have also to specify the step  (24)?
Thanks!
Alceu

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