[rrd-users] Re: Specification of RRA Boundaries

[Alex van den Bogaerdt]

On Tue, Aug 24, 2004 at 04:11:54PM -0400, Bush, Andrew G  [NY] wrote:

> Your response is appreciated and indeed I have managed to move this
> problem forward somewhat by making the changes suggested. I am however
> now observing a problem that the x-axis start and end times of the chart
> are not lining up with the specified start and end parameters. 
> As you can see (example attached) while the RRA boundaries are now
> correctly aligned (thank you!) the chart is not.

not yet.

> My environment;
> - The specification of the RRD has been modified to have hourly RRAs
> only (daily has been removed).

> - Data is collected every minute.

If you are trying to build images like the one attached
in http://www.ee.ethz.ch/~slist/p/image_7089.png , you probably
do not want to update each minute.

IF you try to do so:
Set heartbeat to a large number (larger than 86400) and update at
midnight only.

> 	RRDs::graph (-imgformat,PNG
> 		--width,500,
> 		--height, 300, 
> 		--step, 86400, 

step 86400 ...

> 		--start, 1092628800,
> 		--end, 1093233600,

... but:

1092628800 mod 86400 != 0  -> cannot work
1093233600 mod 86400 != 0  -> cannot work

RRDtool will modify the start and end so that it _is_ n*86400.

> 		--step 86400,

another step.  Get rid of them both.

> 	1092628800 = Monday 16 August 2004 00:00 EDT (I think!)
> 	1093233600 = Monday 23 August 2004 00:00 EDT (I think!)

if EDT is four hours behind UTC then this is OK.
perl -e 'use POSIX; print ctime(1093233600);'
will show the wall clock time.

HTH
Alex
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