[rrd-users] trying to understand the relationship between source data, what's in rrd and what gets plotted

Alex van den Bogaerdt alex at ergens.op.het.net
Wed Jul 25 14:04:44 CEST 2007

On Wed, Jul 25, 2007 at 07:43:50AM -0400, Mark Seger wrote:

> > "Nearest minute boundary":  No, it does not.  You tell it where to
> > do so, using "--step".
> >   
> Maybe I misled you by the term 'minute boundary', but I meant that it 
> appeared to align the data such that at least one sample fell on a 
> minute boundary which is consistent with an earlier reply made by 'Simon 
> Hobson' in which he said

Change your "--step" to something different.

> yes, and that confirms what I think I also said.  rrd picks the times of 
> the intervals for you using YOUR stepsize but ITS times, so if my 
> samples are every 10 seconds starting 6 seconds after the minute, none 
> of my data points will be recorded exactly as I supplied them.  I 

That is because hh:mm:06, hh:mm:16, hh:mm:26 and so on are not a whole
multiple of 10 seconds.

You have "n*step+offset", not "n*step".  This is why normalization is

> As I said above it sounds like if I conform my data to align to the time 
> boudary conditions rrd requires it should work and if I don't conform it 
> won't.

No.  Your step size is wrong, not your input.  Change your step size
to 1,2,3 or 6 seconds.

Alex van den Bogaerdt

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