[rrd-users] Re: AW: Re: problem with manual reset - suggestion

[Alex van den Bogaerdt]

On Mon, Dec 09, 2002 at 04:34:03PM +0100, Pressler Florian, DI wrote:

> I'll clear counters by calling a function which does:
> 
> 1. Get actual time (z)
> 2. Retrieve & write actual value of counter to rrd at z-3
> 3. Reset counter on device
> 4. Write "unknown" value to rrd at z-2
> 5. Write '0' value to rrd at z-1

This should work and yes, it will result in a minimal amount
of "unknown" data.  However, I don't think you should use
the "z-1" time.

An update at time "z" describes the time *before* time "z".
The period between "z" and the next update is described by
the next update.

A cron job will:
a) run at exactly "z" and therefore return "0" as the counter value;
   in this case you would try and enter the same data twice (one of
   them failing, no problem)
or
b) run after "z" and thus there's no problem.


> As far as I have understood the manual of RRDtool, the setting of
> heartbeat (in my case 120) should not prevent above theorie from
> working. What I did not quite understand is the meaning of xxf. It is
> set to 0.5 at the moment - could this lead to a problem?

xff is used at consolidation.  If RRDtool needs more than one PDP
(normalized interval) to build a CDP, chances are that one or more
of these PDPs are unknown.  xff determines how much of the data is
allowed to be unknown and still produce a valid CDP.

HTH
Alex

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