[rrd-users] Graph strange lag on datas

Simon Hobson linux at thehobsons.co.uk
Mon Mar 7 18:06:33 CET 2011

Tntteam wrote:

>I have a strange behavior on my graphs.
>Here is the data source I use to generate the graph :
>As you see I inserted manually a 10 value to generate a high point 
>in the graph.
>The timestamp 1299062660 is 11:44:20 (GMT +1)
>Now is the output rrd graph :
>And my rrd definition :
>rrdtool info 1.rrd :
>filename = "1.rrd"
>rrd_version = "0003"
>step = 60

In RRD databases, ALL intervals are based on Unix epoch (midnight 1st 
Jan 1970 UTC). So your steps all end on the minute - not at 20s past 
the minute. SO your burst to a higher value is normalised so that 40s 
worth goes into the period ending at 11:44, and the other 20s worth 
goes into the next step.

So your graph is quite correct.

For more detailed explanation, see Alex's tutorials at :
in particular the one on normalisation and consolidation.

BTW - full marks for providing the exact data used for the test, the 
definition of your file, the actual output, and a description of what 
you expected. Most people omit 2 or 3 of those items !

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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