[rrd-users] Re: Difference between the values read and the values stored

[Alex van den Bogaerdt]

On Tue, Sep 23, 2003 at 01:32:51PM +0200, David Knecht wrote:

> I'd like Cacti 0.8.3 and RRDtool 1.0.39 to store and graph ***exactly*** 
> the value that it gets as its input.

Then you have to tell RRDtool to store at ***exactly*** the right time.


> As you can see there is a slight difference between what Cacti reports 
> and what rrdtool stores/graphs (in fact, each value differs towards its 
> preceding value).

Normalization.

> Does this mean that RRDTool does not/cannot store values in its raw 
> form, even if using GAUGE data types? Is it correct that RRDTool is 
> doing some time compensation even for GAUGE data types (which to my 
> latest understanding are not related to time?) Might any other averaging 
> mechanism fool me here?

COUNTER ->    rate = delta(counter)/delta(time)
ABSOLUTE ->   rate = (value)/delta(time)
GAUGE ->      rate = value.

Then:

rate -> normalization -> RRA.


*If cacti is using something similar to "rrdtool update N:12345" then
what is "N"?

N is approximately "09/22/2003 9:40 AM".  N is not exactly "09/22/2003 9:40 AM"

HTH
Alex

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