In some basic tests that I performed directly graphing the an RRD by command line, I notice that graphs that use the AVERAGE Data Point will show fluctuation in the max listing. If you create a graph using the MAX data point, the max value should stay the same as you increase the time span.
The default RRD database settings have different recording characteristics for displaying graphs for data hourly, weekly, monthly and yearly (These are the default RRA definitions in your performance monitor). Let's focus on the weekly display. By default, Zenoss is configured to say, collect 24 samples (two hours at 5 minute intervals) and record the AVERAGE of the sample set and the MAXIMUM value of that sample set. The RRDGraph command will attempt to select the RRA Data set that most closely matches the resolution you have chosen to display. Normally, your zoom will stay with the same data set, until the time frame exceeds the amount available in the data set, or the when the resolution of another data set closely matches that of the graph. So if your graph is 350 pixels wide and you are displaying a weeks worth of results, it will select the RRA that provides a minimum of 50 data points per day and holds a weeks worth of data. If you display two weeks of data, to keep the same resolution, you would need to double the width of the graph, or if you keep the same pixel width, it could choose a RRA data set that only has 25 data points per day. Additionally, the resolution for the height also comes into play in selecting which RRA data set to use. Now say that you use an RRA data set with a short frequency (I.E. 5 minutes per record). And you are displaying a long period of time. If you hit the point where there are two data points available for each pixel, guess what happens. The first two values get paired and averaged. Then the next two. So if you have a max value in one data point, it gets watered down as it is averaged with the next data point. You can try to take the height value out of the decision about which RRA data set to choose by setting the max and minimum value to display in the graph. This will mean that the Y-Axis scale will not be auto-scaled and variable (because Zenoss should include the --rigid flag in the graph command). But the only real way to be sure that the max does not get averaged would be to include enough RRA statements to cover the most common viewing time frames. The default RRA statements were determined with a 5 minute step in mind. If you shorten the SNMP cycle time in your performance monitor you should adjust the RRA statements to be more appropriate. On Thu, 2007-07-12 at 19:02 +0000, agthurber wrote: > I noticed when you zoom out on a graph that it seems to average out the data > and you loose the highest values. Is there any way to force the graphs to > retain the max values? > > ------------------------ > A. G. Thurber > > > > > -------------------- m2f -------------------- > > Read this topic online here: > http://community.zenoss.com/forums/viewtopic.php?p=8672#8672 > > -------------------- m2f -------------------- > > > > _______________________________________________ > zenoss-users mailing list > [email protected] > http://lists.zenoss.org/mailman/listinfo/zenoss-users -- James D. Roman IT Network Administration Terranet Inc.On contract to: Science Systems and Applications, Inc. _______________________________________________ zenoss-users mailing list [email protected] http://lists.zenoss.org/mailman/listinfo/zenoss-users
