Hi Lutz, This is probably a result of consolidation (and Averaging) that occurs when several samples is combined when RRD-tool creates the graph. It does this when it finds out that you have more values available - than what you have pixels in the graph.
You can see the result of the averaged/consolidated Max and Min values compared to the Max of Max and Min of Min-values in the following graph. http://stats.villaelmerfjord.se/test_minmax-am18_week19_hourly.png We have 5 years of 5 minute resolution - so no consolidation occurs in the data-files. Even if you have a Average RRD, you can get (and keep) the max and min-values if you override the default consolidation method. The above graph was created with the following arguments. rrdtool graph test_minmax-am18_week19_full.png --imgformat PNG -s 1367791200 -e 1368396000 --height=700 --width 1600 \ DEF:ds0=/home/httpd2/htdocs/admin/power/am18-temp_fahrenheit.rrd:ds0:AVERAGE \ DEF:ds0max=/home/httpd2/htdocs/admin/power/am18-temp_fahrenheit.rrd:ds0:AVERAGE:reduce=MAX \ DEF:ds0min=/home/httpd2/htdocs/admin/power/am18-temp_fahrenheit.rrd:ds0:AVERAGE:reduce=MIN \ VDEF:ds0avg=ds0,AVERAGE \ VDEF:ds0avgmax=ds0,MAXIMUM \ VDEF:ds0avgmin=ds0,MINIMUM \ VDEF:ds0maxmax=ds0max,MAXIMUM \ VDEF:ds0minmin=ds0min,MINIMUM \ VDEF:ds0pct=ds0,95,PERCENT \ LINE1:ds0#0000FF:"Temperature" \ LINE1:ds0max#FF0000:"Temp Max" \ LINE1:ds0min#00FF00:"Temp Min" \ LINE1:ds0avgmax#FF0050:"Temp Avg Max" \ LINE1:ds0avgmin#00FFA0:"Temp Avg Min" \ LINE1:ds0maxmax#FF50A0:"Temp Max of Max" \ LINE1:ds0minmin#50FFA0:"Temp Min of Min" \ LINE1:ds0pct#101010:"95 Percentile\l" \ COMMENT:" \l" \ COMMENT:"Average " \ COMMENT:"MaxAverage " \ COMMENT:"MinAverage " \ COMMENT:"MaxOfMax " \ COMMENT:"MinOfMin " \ COMMENT:"95th percentile\l" \ GPRINT:ds0avg:"%6.2lf %SdegF" \ GPRINT:ds0avgmax:"%6.2lf %SdegF" \ GPRINT:ds0avgmin:"%6.2lf %SdegF" \ GPRINT:ds0maxmax:"%6.2lf %SdegF" \ GPRINT:ds0minmin:"%6.2lf %SdegF" \ GPRINT:ds0pct:"%6.2lf %SdegF\l" The important thing here is the additional DEFS I create where I specify the reduce functions. (to override the default AVERAGE that is specified in our RRDs). The last part is just for printing the different values under the graph. /Johan -- Johan Elmerfjord | Sr. Systems Administration/Mgr, EMEA | Adobe Systems, Product Technical Operations | p. +45 3231 6008 | x86008 | cell. +46 735 101 444 | [email protected] On Wed, 2013-09-11 at 02:07 -0700, Lutz Schulze wrote: > Hello, > > we use RRDTools with an own PHP script and generate graphs at this > way: > > $options = ""; > $options .= " $img_file"; > $options .= " -t \"$vdesc\t$desc2\" "; > $options .= " --start $start"; > $options .= " --end $end"; > $options .= " -w $width"; > $options .= " -h $height"; > $options .= " --slope-mode"; > $options .= " -c SHADEA#f0f0f0 "; > $options .= " -c SHADEB#f0f0f0 "; > $options .= " -W ".$config['watermark']; > $options .= " -c ARROW#58A6A7 "; > $options .= " DEF:$val=$rrd_file:$sid:AVERAGE"; > $options .= " LINE2:$val$color[$i]:\"$beschreibung\" "; > $options .= " GPRINT:$val:LAST:\"%4.1lf\""; > $options .= " GPRINT:$val:MIN:\"min %4.1lf%s\""; > $options .= " GPRINT:$val:MAX:\"max %4.1lf%s\l\""; > > popen(RRDTOOL." graph $options", "r"); > > When we now generate graphs with different sizes unfortunately the > values for LAST, MIN and MAX change also: > > small picture: > http://km2.klima-monitor.de/system.graph.php?mode=view&vid=3&t=y&se=2&start=01.01.2013&end=01.01.2014&width=429&height=200 > > big picture: > http://km2.klima-monitor.de/system.graph.php?mode=view&vid=3&t=y&se=2&start=01.01.2013&end=01.01.2014&width=837&height=400 > > > I think it is a problem with sampling the used values from the > archive. Is there a way to make this better? > > Thank you for all help > > Lutz
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