[rrd-users] DEF/CDEF Average Question

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Thu Mar 24 23:55:16 CET 2011

----- Original Message ----- 
From: "Chris Nighswonger" <cnighswonger at foundations.edu>
To: <rrd-users at lists.oetiker.ch>
Sent: Thursday, March 24, 2011 6:47 PM
Subject: [rrd-users] DEF/CDEF Average Question

>I have data that I want to average in 15 min windows. The caveat here
> is that the windows must start at 0 min, 15 min, 30 min, and 45 min of
> each hour.
> I can do
> DEF:x=foo.rrd:bar:AVERAGE:step=900
> But if foo.rrd starts at 5 min past the hour, my window is skewed.

If you have an RRA with step*steps == 900, then RRDtool will do the work for 
For instance: if step==300 (5 minutes) and steps==3, the time in each RRA 
row is 900 seconds. All rows will start at n*300, which happens to be hh:00, 
hh:15, hh:30 and hh:45.


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