[rrd-users] Direct RRA updates

Milan Krčmář krcmar at datinel.cz
Sun Nov 13 19:00:44 CET 2011


I have the following idea: I would like to store statistics of a
network interface (throughput in megabits per second) using RRD. Say
the appropriate DS would be updated in minute intervals (it would have
"step" set to 60 seconds). But the software which gathers the stats is
able to read counters more frequently (for example once in every
second), so it does not get only total (average) throughput for whole
60 seconds, but also minimum and maximum throughput withing the 60
seconds (with 1 second time slot). Is there any possibility to store
this information to the RRD as well?

A similar scenario: ping a host every second but store only
min/max/avg values every minute.

I would like to create a single RRD file with step=60,
RRA:MIN:steps=1, RRA:MAX:steps=1, RRA:AVERAGE:steps=1 and have all the
RRAs updated in every step (providing 3 values).

I know there is still possibility to create three RRD files, one for
MIN, the second for MAX and third for AVERAGE, since all DSes in a
single file share all RRA definitions, but is there a better solution?
(Also, I don't want to simply set step to 1 second and update the file
60 times per minute).

A side note: why, under usual conditions (not the example above),
should I define RRAs with steps=1 for all the aggregates I want to
then use with steps>1? (examine any RRD file with "rrdtool info" to
see several RRAs with steps=1). RRA with steps=1 does not consolidate
data, it only stores them: it is enough to have only one such a RRA...


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