[rrd-developers] Re: (bug?) Incorrectly selecting low-res RRA

[Phil Radden]

On Thu, 27 Mar 2003, Alex van den Bogaerdt wrote:
> Try specifying "--end xxx" with xxx being a multiple of 10080.
> The amount of rows should be low.  For instance:
> 
> ...fetch...  --start end-50400 --end 1048783680
> 
> Now do the same query with "--start end-2419200" and adjust
> the end time to be the largest number being a whole multiple
> of 10080 but not being later than "now".
> 
> Then do the same exercise with some number that is a multiple
> of 86400.  You should see the pattern eventually.

Hi again,

You'll be delighted to hear that I finally understood exactly what was 
going on over the weekend, and given my two RRAs with sample periods being 
10080 seconds and 86400 seconds, it'll chose the 'wrong' one in exactly 
those circumstances where
  NOW % 86400  <  NOW % 10080

(Presumably, the creation time of an rrd is irrelevant, it always chunks 
time based on time-since-epoch modulo sample period?)

As suggested, I'll amend the query (via rrdtool graph) so that it uses a 
multiple of 10080 as the endpoint of the plot, in which circumstances it 
always does what I want it to.

Thanks very much!
Phil

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