When I say tune, I mean utilizing rrdtune and rrdresize to affect 
changes to the RRD file. I suspected the file was fixed, but wanted a 
little bit more assurance. Thanks for the response.

On 6/19/2014 10:59 AM, Simon Hobson wrote:
> Kevin Stewart <[email protected]> wrote:
>
>> Once an RRD is created, as points are added, will the file grow over
>> time? Or does the file stay the same size (given that is is not tuned)?
> As Pablo says, they are pre-allocated and stay the same size - that size is 
> known because you define all the DSs (data series), consolidations, and 
> retention periods (ie number of consolidated data points to keep) when you 
> create the file. Internally it is as the name says, a round robin. Each 
> consolidated data set is defined by a single list of values - plus a pointer 
> to the current "start/end". As new data comes in, it simply over-writes the 
> oldest data and the pointer moved on - when the pointer gets to the end, it 
> wraps around to the beginning. So nothing is "added" or "removed" - only 
> updated in-place.
>
> However I'm not sure what you mean by "not tuned" - because RRD files are 
> actually quite highly tuned for a specific purpose, that of efficiently 
> storing/extracting/graphing predefined sets of data as above.
>
> As a bit of trivia, RRD Tools came out of the MRTG project - a set of tools 
> to collect, consolidate, and graph interface traffic rates for routers (hence 
> Multi Router Traffic Grapher).
>
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