[mrtg] Re: can i keep more data

[Alex van den Bogaerdt]

On Sun, Oct 27, 2002 at 09:58:24AM -0500, Chris Robb wrote:

> But I've run into a problem with the graphs since performing the RRA
> resize. I'm using the rrdcgi program to mimic MRTG's generated graph page.
> 
> Notice that the weekly, monthly and daily graphs don't show data past 2.5
> days from the current time.

> I might understand this better if I knew how RRD chooses which RRA to look
> at when creating a graph.

You're on the right track.

The problem is in the way you query the RRD.  If you don't ask for
an exact match, RRDtool will have to do a best match.

Data is *always* there.  It may be unknown yet it is there.

If you query for "--end now" and "now" happens to be 23:06 then 23:05 is
a better match than 23:00, 22:30 or even 22:00.

Try the difference between asking for the following time ranges using fetch:

--start end-1d --end 00:00
--start end-1d --end 00:30
--start end-1d --end 02:00
--start end-1d --end hh:mm

In this last line, fill in a time such that your local time equals 00:00 UTC.
(I guess this will be 19:00)

The fetch command should resemble
"rrdtool fetch mydata.rrd AVERAGE --start end-1d --end 00:00"

Try some more combinations of start and end.  Also do the same for a graph
command.  If necessary read the tutorial.

HTH
Alex

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