[rrd-users] A reason there isn't a CF SUM function?

Rafal Gwizdala rafal.gwizdala at gmail.com
Tue Aug 21 21:17:44 CEST 2012

On Tue, Aug 21, 2012 at 8:00 PM, Simon Hobson <linux at thehobsons.co.uk>wrote:

> Which you can get with :
> cdef:data_sums=data_avg,${res_step},*
> Where ${res_step} is the length of the consolidation interval being
> used. In your example, 1800 seconds.
> What might be more useful might be an option to handle unknowns
> differently during consolidation.
> the only problem is that when rrdtool selects the consolidation interval
automatically you have no easy way to obtain that value in your cdef
calculation. Even if you specify the interval in the command line, rrdtool
can silently use a larger value if RRA data resolution is lower than
specified and you'll get invalid sums on the graph.
And I'm not yet sure what to do with unknowns - probably you could prevent
unknowns by using large heartbeat parameter during rrd creation and large
xfiles factor for RRAs
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