Re: How does cacti calculates AVG?

Thanks Gandalf..
the problem was solved..
the problem was that I had some "nan" values on my rrd file... as I could
see, cacti ignores these values on the AVG ... so if I have 5 values, one
of them is nan, to cacti I have only 4 values..
(it sums the 4 values and divide by 4)
my script was considering nan values as 0, so I had 5 values
(it sums the 5 values - one of them is -, so I have the same 4 values than
cacti consider - and divide by 5) ..
that's why I was getting a different value..

it was solved with a simple grep -v on my script...lol


thanks again Gandalf...


2012/3/16 Gandalf <[email protected]>

> Ok, this is the standard rrdtool AVERAGE, that is used here.
> Find some hints for that at http://www.vandenbogaerdt.nl that describes
> quite
> well what is happening here. Or consult the rrdtool man-pages and/or the
> web
> site. There's nothing Cacti does here apart from plain rrdtool
> Reinhard
>
> On 16.03.2012 13:43, Andre Luis wrote:
> > /usr/bin/rrdtool graph - \
> > --imgformat=PNG \
> > --start=1331809200 \
> > --end=1331845200 \
> > --title="Oracle - sessions RAC" \
> > --base=1000 \
> > --height=120 \
> > --width=500 \
> > --alt-autoscale-max \
> > --lower-limit=0 \
> > COMMENT:"From 2012/03/15 08\:00\:00 To 2012/03/15 18\:00\:00\c" \
> > COMMENT:"  \n" \
> > --vertical-label="" \
> > --slope-mode \
> > --font TITLE:12: \
> > --font AXIS:8: \
> > --font LEGEND:10: \
> > --font UNIT:8: \
> >
> DEF:a="/opt/collectd/var/lib/collectd/srv-rac01/oracle-OracleDatabase/gauge-Oracle-Sessions.rrd":value:AVERAGE
> > \
> > LINE2:a#FF0000FF:"Sessions\:"  \
> > GPRINT:a:LAST:"Current\:%8.0lf"  \
> > GPRINT:a:MAX:"Max\:%8.0lf"  \
> > GPRINT:a:AVERAGE:"Avg\:%8.0lf\n"
> >
> >
> > 2012/3/15 Gandalf <[email protected]>
> >
> >> There are two different ways of printing an AVG with cacti. Please
> provide
> >> the
> >> rrdtool graph statement used to clarify. Goto Graph Management and
> switch
> >> to
> >> DEBUG to see that statement
> >> Reinhard
> >>
> >> On 15.03.2012 20:25, Andre Luis wrote:
> >>> I am monitoring the number of sessions on a database.
> >>> now I am seeing On the graph on the period of 2012-03-14 00:00 to
> >>> 2012-03-15:00 ... and the avg on the graph is 200 sessions on this
> >> period...
> >>> but if I sum all the data stored on the rrd on the same period (using
> >>> rrdtool fetch), then divide by number of the datas, then I got
> something
> >>> about 100 sessions..
> >>>
> >>> anyone knows why is this happening?
> >>> so, how does cacti calculates the AVG?
> >>>
> >>
> >>
> >>
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