[rrd-users] Re: rrdcgi problem with picture.

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Mon Nov 26 13:57:54 MET 2001

Nuno Emanuel Rodrigues wrote:

> About my rrd configuration, i think i did the correct configuration, i have
> a rra with 105408 rows , 1 PDP ... so  i have a full year of "exact" values.

I think you have what you need to have.  You have a pretty good understanding
of RRDtool, don't let others fool you.

> My graphs webpages has 4 grahics, a daily, 1 weekly, 1 monthly and 1
> yearly... and my purpose is.. the user see on the month or yearly graphic a
> interesting range of time... (lets say 2 days) and he wants to see the exact
> values, not 30 minutes averages, so using the rra i mentioned before, he can
> generate the graphic, or maybe do a database dump to a xml file of the
> specified time period.

That's possible, as long as the users understand that
 a) you can't get data from the RRA that isn't in there
 b) you can't get the data at a resolution that isn't in there

Assuming you are working with 5 minute PDPs:
5 months ago to (5 months - 3000 minutes) ago at a resolution of
5 minutes per pixel on a graph of 600 pixels is perfectly doable.

> One interesting thing, is that i had a rrd with the big rra i mentioned and
> 3 more rras, 1 for the week, month and year, with week (30 minute avg),
> month (2 hour avg), and year (1 day avg) like Paul said.
> But in the week graph, rrdtool used my first RRA, instead of the week (30
> minutes avg) RRA....

Try setting start and end times.  Do this on twice, one time using correct
boundaries and one time using incorrect boundaries (on purpose).
What I mean is: for a graph width of 600 pixels and a pixel span of 30
minutes, the total graph time becomes 1800 minutes. The "weekly RRA" has
data at 30 minute intervals; it will know about 00:00 to 00:30 and not
about 00:05 to 00:35.
--start 20011126 00:00 --end start+18000min
--start 20011126 00:05 --end start+18000min
Check if you find any differences in cpu-time consumed. 

> Other point where i would like to get some feedback is: Using a setup like
> this... just 1 RRA, with no consolidation at all.. generating a week,month
> and year graph every 5 minutes (running from cron) : 
> 	-all the consolidation is done when the grahs are constructed ?

> 	-Wont be to much cpu consuming, if i have ...20 or 30 rrds,
> generating new graphs every 5 minutes with this setup?
that depends on your definition of "too much".  Also, it doesn't
depend on the number of RRDs, it depends on the number of DSes to graph.

> And finally...returning to my RRDCGI Problem...i still have the problem of
> rrdcgi generating the pictures with this attributes :
> -rw--r--r--    1 apache   apache
> And when i run the rrdcgi again he cant overwrite the picture... and no
> picture is created.. would like some help with this.

rrdcgi is run by the apache daemon.  The apache daemon creates the file.
It seems strange to me that this same apache daemon cannot overwrite the
file.  Are you sure it's not a caching problem or maybe a "--lazy" switch
is being used ?

> P.S. A RRD with only a RRA with 105408 rows (1 PDP) is not all that big, its
> just 1,687,380 byes ....shouldnt be bigger?

105408 rows,1 value per row, times 4 bytes per value --> 421632 bytes.

If you only have one RRA and one DS per RRA, the file is too big.
It seems that the product of DS and RRA is 4 (i.e. you have 1 DS and
4 RRAs, 2 and 2, or 4 and 1).

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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