[rrd-users] Re: averaged history dampens spikes

Michael Van Camp mcamp at alchemy.net
Wed Aug 16 06:47:54 MEST 2000

Yep, I have seen the same thing... and spikes are important to me too.  I am
not actually using cricket, but RRDtool and my own scripts.

The problem with a default data config with RRA's progressively decreasing
the frequency of your data points into the past is that, logically enough,
AVERAGEing brings down your spikes.  Since spikes are often valid data that
I need to know about, I just use MAX as a consolidation function, and keep a
year's worth of data.  Yeah, at 300 second steps thats a 1.8 MB file, but
disk space is cheap, and it is still better than storing my data in a MySQL
database.  I also keep decreasing RRAs as in the examples, since they don't
take up much space, but unfortunately for my purposes, they lie.  ;-)

So I pay more attention to MAX data.  Comments?   I guess it depends on how
much you care about valid spikes.

Yes, yes, I know for consolidation on 1 data point it doesn't matter what CF
you pick, its just the exact data, but I sample some ports every minute for
two days and consolidate them to every five minutes.

I am also curious what Tobi thinks of the performance hit of graphing
against every data point for a year rather than consolidated data.  Since I
prefer MAX to AVERAGE, should I be consolidating my data down with MAX
still?  Most of my graphing is of the last two days anyway.

----- Original Message -----
From: <cricket-users-admin at lists.sourceforge.net>
To: <cricket-users at lists.sourceforge.net>
Sent: Thursday, August 17, 2000 3:09 AM
Subject: cricket-users digest, Vol 1 #214 - 6 msgs
> Message: 1
> Date: Wed, 16 Aug 2000 13:06:50 -0400 (EDT)
> From: Keith Makuck <makuck at email.unc.edu>
> To: cricket-users at lists.sourceforge.net
> Subject: [cricket-users] Graphs aren't precise for history
> I combed the archives, so if I've missed the answer to this, I apologize.
> I'm graphing ifInOctets and ifOutOctets of some switches and
> routers.  I'm only graphing one target per graph -- nothing fancy.  Only
> thing I've changed from defaults is the sampling, which is every 120
> seconds.
> If you look at the "Average bits in" and "Cur", the value is 25.0
> Mbits/sec. (for example)  Let's also say that it says the max is 50.0
> Mb/sec.  Well, when you look at the Hourly graph, the line denoting the
> current value is correct.  But, looking back at the history of the hourly
> graph, the general ups and downs are right, but the peak never actually
> gets to 50.0 Mb/sec.  Same is true for "Average bits out" as well.
> This happens to all of my graphs and is quite perplexing.  Ideas?

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