[rrd-users] Help with RRD.... in over my head

Steve Shipway s.shipway at auckland.ac.nz
Thu Jan 19 22:55:58 CET 2012

You are not entering enough values to get a complete cdp.


This is important:

--start 1325232008 --step 180 \




What this says is the STEP of the RRD is 180 seconds, or 3 minutes (often,
people will use 1min or 5min).


You are only STORING the data in a single RRA, which  has 10,000 cdp lines,
where each cdp (consolidated data point) is the AVERAGE of 20 dps (data


So, you need to write 20 data points, at 3min intervals, before you get ONE
cdp stored.  Your xff is 0.5 which means that a cdp will remain unknown
until at least 50% (IE, 10) points are written.


This means you will get NaN output from your fetch until you have done at
least 30 mins of data!


Your test data had only 2 data points, and they are only 21 seconds apart,
so the second would be ignored anyway.  Try entering in at least 10 dps,
with time intervals of 180, and you should start seeing a single cdp on your


I suspect you are not setting the step or RRA parameters appropriately.
Maybe try an additional RRA with AVERAGE:0.5:1:10000 (so each data point is
stored),  and/or decrease the step?





Steve Shipway

ITS Unix Services Design Lead

University of Auckland, New Zealand

Floor 1, 58 Symonds Street, Auckland

Phone: +64 (0)9 3737599 ext 86487

DDI: +64 (0)9 924 6487

Mobile: +64 (0)21 753 189

Email:  <mailto:s.shipway at auckland.ac.nz> s.shipway at auckland.ac.nz

P Please consider the environment before printing this e-mail 



From: v g [mailto:infiniteseeker at gmail.com] 
Sent: Friday, 20 January 2012 6:56 a.m.
To: Steve Shipway
Cc: rrd-users at lists.oetiker.ch
Subject: Re: [rrd-users] Help with RRD.... in over my head




Thanks for your reply.  Still having an issue but managed to isolate it
further.  It looks like it enters the first update correctly and then fails
on the subsequent ones.  Obviously, I am not doing something correct but I
cant figure out what.  




Here is what I did as per your suggestion:


Creating RRD file:


rdtool create birken-boiler.rrd \

--start 1325232008 --step 180 \

DS:boiler_out_flow:GAUGE:600:0:U \

DS:boiler_in_flow:GAUGE:600:0:U  \

DS:vihara_in_flow:GAUGE:600:0:U  \

DS:vihara_out_flow:GAUGE:600:0:U \

DS:outbldg_in_flow:GAUGE:600:0:U  \

DS:outbldg_out_flow:GAUGE:600:0:U  \

DS:cistern_top:GAUGE:600:0:U  \

DS:cistern_bottom:GAUGE:600:0:U  \

DS:boiler_flow_gpm:GAUGE:600:0:U  \

DS:vihara_flow_gpm:GAUGE:600:0:U \

DS:outbldg_flow:GAUGE:600:0:U  \

DS:boiler_btu_per_hr:GAUGE:600:0:U  \

DS:vihara_btu_per_hr:GAUGE:600:0:U  \

DS:outbldg_btu_per_hr:GAUGE:600:0:U \



Entering in Values:


rrdtool updatev birken-boiler.rrd

rrdtool updatev birken-boiler.rrd




return_value = 0

[1325235600]RRA[AVERAGE][20]DS[boiler_out_flow] = NaN

[1325235600]RRA[AVERAGE][20]DS[boiler_in_flow] = NaN

[1325235600]RRA[AVERAGE][20]DS[vihara_in_flow] = NaN


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