[rrd-users] cant get to understand described normalization behaviour

[Peter Thurner]

perfect explaination! thank you very much!

last thing I dont get is the fact that all the data now is moved by 5
minutes to the right or so..

I attached the new, fixed script.




On 03/26/2014 10:47 AM, Alex van den Bogaerdt wrote:
> I think you're missing the fact that RRDtool uses timestamps based on UTC.
> When you specify "--step 86400" you are telling RRDtool to create a database 
> with start and end times which are a whole multiple of 86400 seconds.
> 
> Your first timestamp is 1395140400 which is n*86400+39600.
> Your second timestamp is 1395226800 which also is n*86400+39600.
> I did not check the rest but I can safely assume the rest will not be 
> different.
> 
> Normalization massages the input so that it fits in (n-1)*86400 to n*86400 
> time intervals.
> 
> The rate computed at 1395226800 is valid partially in the interval upto 
> 1395187200 and partially thereafter. To be precise, (86400-39600)/86400 
> stays in the timeslot computed for 1395187200 and 39600/86400 goes to the 
> next timeslot.
> 
> Your next update is at time 1395313200. Now there is enough data to compute 
> the timeslot between 1395187200 and 1395273600. The rate logged at time 
> 139573600 should be 39600/86400 * 3 + 46800/86400 * 2 = 2.458333....
> 
> HTH
> Alex
> 
> 
> ----- Original Message ----- 
> From: "Peter Thurner" <p.thurner at heinlein-support.de>
> To: <rrd-users at lists.oetiker.ch>
> Sent: Wednesday, March 26, 2014 10:24 AM
> Subject: [rrd-users] cant get to understand described normalization 
> behaviour
> 
> 
> Hi guys,
> 
> I'm kind of dying on this one. I attached 3 bash scripts that show where
> I don't understand things anymore. I guess its quite simple.
> 
> I feed the same values using the same CF and RRD specs everywhere, but
> on the script rrdtest-days.sh, I get a graph that is a lot different to
> the other two scripts.
> Other than the --step size I did not change much (as a diff would show).
> 
> Why (and how?) is it normalizing when all I increase is the timespan
> between updates? I'm sure I missed something..
> 
> Thank you very much in advance! :)
> 
> Peter
> 
> 
> 
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