[rrd-users] What if interval of data reads varies

Steve Shipway s.shipway at auckland.ac.nz
Tue Jun 17 00:01:52 CEST 2014

If your data are arriving at irregular intervals, then RRDTool will use Data Normalisation to convert them into step-based intervals.  Note that this will mean the data in specific samples of the RRA is not necessarily the same as the data you supplied, though averages and totals will remain accurate.  Make sure you understand this behaviour; if it is not what you want, and you need to keep your samples at their irregular time points, then RRDTool is not the tool for you.


So, you should set your Step interval based on the average rate at which you expect the data to arrive, or maybe slightly less – for example, if the data will normally arrive at approximately 6minute intervals, but could be in the range 4min – 10 min, then I’d set the Step interval to 5minutes, since it is most helpful if the Step perfectly divides into an hour (so try steps of 1min, 5min, 10min, 15min…).  This allows you to keep the best resolution of data, and to create roll-up RRAs of a convenient consolidated step size.


You should make sure to set the Heartbeat of the Data Source to be the maximum time expected between data samples (maybe plus a bit).  So, in the example above where data samples are expected to arrive at something like 4min – 10min intervals, set the Heartbeat to be 10min or even slightly longer.  If a sample arrives after this time, an ‘unknown’ will be inserted for the gap.






Steve Shipway

s.shipway at auckland.ac.nz


From: rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch [mailto:rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] On Behalf Of Steven Sim
Sent: Tuesday, 17 June 2014 2:41 a.m.
To: rrd-users at lists.oetiker.ch
Subject: [rrd-users] What if interval of data reads varies



What if my data is provided at an interval which is not regular?


I put the maximum interval as the interval to step in rrdtool create?


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