[rrd-users] Re: rrdtool create

[Alex van den Bogaerdt]

On Wed, Dec 08, 2004 at 04:26:07PM +0100, Georges Toth wrote:

> i'm monitoring a traffic counter, which gets reset by the end of the month (so 
> not at the 32 or 64bit boundary).
> what datasource type should i use for that?

Counter, or derive.

> i tried counter, but when the month is over, the graph looks very strange if i 
> graph some hours before and after the reset, in one graph.

You didn't set a proper maximum, or your counter increases to _almost_ the
full value in one month.

The resulting rate will be way too high, because RRDtool thinks it
witnessed a counter wrap.

Solutions:

#1 Just before the counter gets reset, update your database. One
   second later, update the database with "U" (for unknown).
   Another second later (preferably exactly when the counter is reset)
   update the database with zero.

   This way you have the most accurate results

#2 Use DERIVE as your datasource type.  When the counter is reset, RRDtool
   will see this as a negative rate.  Tell RRDtool it should not accept
   negative rates (minimum value set to zero)

HTH
Alex
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