[rrd-users] odd XPORT results

Dave Whitehead DaveW at marwell.org.uk
Mon Jun 13 16:19:01 CEST 2011



I'm puzzled by my results when extracting data from an RRD which stores
power usage in kW from several sensors. They are spot values and are not
constantly increasing like a router byte counter. This is RRD 1.2 on
Windows x86 by the way.


The RRD definition is this.... 


rrdtool create kwh.rrd --start N --step 300 









Which as I understand it should maintain the data with two averages for
each sensor. 

One average should be for every 5 minutes for 105120 samples (approx 1
years worth)

The other should store 1hrly for 43800 samples (approx 5 years worth)


The data collection has been running since approx May 2010 so I was
expecting to be able to dump either 5min averages (back to Jun 12ish
2010 - a yrs worth) or the full 1hrly averages right back to May 2010. I
realise its averaged data and not actual data values - thats fine.


If I dump the data using RRDTOOL DUMP I can see all the data as I expect
it. (5 min and 1 hr intervals all ok)


The problem I am having is getting the data exported using RRDTOOL XPORT
- no matter what step I give it seems to be in 36000 steps and I cant
get either 5 min or 1hr steps.......


The output command I'm using is (eg)


rrdtool xport -s Jan_1 -e Jun_6 --step 300
DEF:graze=kwh.rrd:graze_0:AVERAGE XPORT:graze:graze


Which gets me this



step: 36000

<?xml version="1.0" encoding="ISO-8859-1"?>



































Why is the step size so large? I'm sure I'm doing something stupid .....










Dave Whitehead | IT & Telecomms Manager | Marwell Wildlife | Colden
Common | Winchester | SO21 1JH

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