[rrd-users] Optimize RRD update

[Sam Umbach]

On Feb 5, 2008 7:31 AM, Gwenael Lahay <gwenael.lahay at wanadoo.fr> wrote:
> Hi,
>
> I have an another (last) question.
>
> When i use a xff of 0.8 for the frequency 5 minutes, the rrdtool does not
> calculate correctly the average if the there is only one value.
>
> For example, if i have the values : 4 Nan Nan Nan Nan
> The stored value for 5 minutes is 4 (4/1) instead of 4/5.
>
> Is it normal and is there a solution ?

This is by design.  Missing data is not (and should not) be treated
the same as zero.  The only way to get the correct average is to enter
the correct data--you need to put zeros in your rrd for each time step
in which the rate is zero.

> Sam had talk about a solution to "collect and batch several RRD updates to
> run at once" but i do not find the information in the archive list. Could
> you indicate me the method.

http://oss.oetiker.ch/rrdtool/doc/rrdupdate.en.html

Look at the example near the bottom of the page.  You can do as many
updates at a time as you want (but you must always insert the oldest
data first).