[rrd-users] Re: Calculating traffic

[Serge Maandag]

Hmm, you're right.

There are moments at which I understand how it works, but I always seem
to mix things up when I haven't read the docs for a while. Perhaps a
somewhat more verbose explanation at the rrdtool website might help.

Serge.

-----Original Message-----
From: Thomas Erskine [mailto:erskine at sourceworks.com] 
Sent: Tuesday, June 25, 2002 5:49 PM
To: Serge Maandag
Subject: Re: [rrd-users] Re: Calculating traffic

<snip>

This isn't the way I understood it, and doesn't agree with my reading of

the docs.  Here's the description of heartbeat:
         heartbeat defines the maximum number of
         seconds that may pass between two updates of
         this data source before the value of the data
         source is assumed to be *UNKNOWN*.

I don't see where you're getting that it will take 10 values to make one

value in the RRD.  The RRA (below) says that one incoming primary data 
point should be used to create one value in the RRD and to keep 100 
value.  The heartbeat is only used to determine how often you have to 
update the RRD.  A heartbeat of 600 means that you must update it at
least 
every 10 minutes or you'll get unknown values inserted.  However, you'll

supply new value every 60 seconds and those will create new value, every
60 
seconds.  The XFF (the 0.5 in the RRA) is for RRAs which do 
consolidation.  An xff of 0.5 means that on half of the values in a
given 
period can be unknown and it will still apply the function (AVERAGE in
this 
case) to the remaining values to produce a consolidated value, but if
more 
than half are unknown, then the consolidated value will also be unknown.

This is my understanding of hw it's supposed to work, and it agrees with
my 
experience in using rrdtool.  If you find differently, please correct
me.


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