[rrd-users] rrdresize on munin-created rrd files

Jacob Alexandersson jacob.alexandersson at aligerum.se
Thu Nov 5 09:57:02 CET 2009

Hello all,

I posted the message below on the munin userlist a couple of days back but I
haven't gotten any response. Hopefully someone can help out here?



Hello all,

I've been digging around a bit on how munin creates its rrd files. I don't
claim to
understand much on the inner workings on rrd, but this is what I've managed
to dig up:

>From my understanding, "rrdtool info <filename>" tells me that the first
three rra's
save one pdp per row, meaning that they don't average out anything. We have
576 rows,
where the "step" is 300 seconds which works out to be 48 hours.

So we have 48 hours of fully accurate data stored (nothing averaged out).

I want "fully accurate" data to be stored much longer. Say 90 days.

90 days = 7776000 seconds. /300 gives me 25920 rows. So I need to add 25344
rows to each rra.
This can be achieved by:

$ rrdtool resize filename.rrd 0 GROW 25344

...where "0" points out the first rra.

I could do this for the first three rra's, but what about the other ones?
There is a set of rra's that store data for 9 days over 30min averages if my
calculations are
correct. This clearly falls within the span of my 90 days above. Will these
rra's ever be used?
Or should I modify these accordingly to something appropriate after my
change above?

I guess what I'm really asking is:
Is this the right way of going about this?

What I am looking for is to store "fully accurate" data for a much longer
time than the (munin)
default of 48 hours.


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