[rrd-users] rrd create --start date; internal treatment

Tobias Oetiker tobi at oetiker.ch
Tue Sep 29 15:02:46 CEST 2009

Hi Filip,

Today Filip Moritz wrote:

> Hi.
> With rrdtool create, --start sets a boundary for the earliest
> accepted values. I assumed this timestamp would be stored inside
> the rrd metadata, now it apears it isn't. Is this correct? Is
> there any way to recover start/creation time from an rrd file?
> Moreover: How is start time treated internally? It seems unknown
> values before start time get involved in aggregation: Time frames
> overlapping start time either become unknown or the unknown
> values padded leading to exaggerated values especially for
> time-series starting with high peaks (here: hits on online news
> articles).

the start time is the 'last update time' if you use rrdtool info.

> Talking workarounds: Is there an option to create rrds with
> pre-zeroed values?

yes, you have to set the start-time as fahr back as you expect the
max update interval to be ...

> Does anyone know good resources or maybe some thread subjects on
> the use of rrd with very infrequent updates?

note that rrdtool  is best suited for regular updates ... (time


Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900

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