[hobbit] data in zoomed graphs

[Henrik Stoerner]

On Thu, Jan 17, 2008 at 03:13:53PM -0500, PAUL WILLIAMSON wrote:
> I have been looking through the docs and know how RRDTool works, 
> but how does the Hobbit zoom function work?  How would I modify 
> the defaults to create RRDs where the 5 minute detail was stored 
> for 6 months?  I can't find the place where I would modify that.  

It is hidden in the RRA parameters used when Hobbit creates the RRD
files. In the 4.3.0 version (and current snapshots) it is configurable,
but in 4.2.0 you must modify the "RRA" definitions in
hobbit-4.2.0/hobbitd/do_rrd.c

6 months = 180 days, each day is 24*60 = 1440 minutes, so for 180 days
of 5-minute details you will need 180*24*60/5 = 51840 datapoints stored.

So you would change the
   static char rra1[] = "RRA:AVERAGE:0.5:1:576";
to
   static char rra1[] = "RRA:AVERAGE:0.5:1:51840";

Note that this is only used when the rrd file is created, so if you want
to apply this to existing RRD files - e.g. to keep the data that has
been collected - you must use the "rrdtool resize"  command to modify
the existing RRD file for the new RRA definition. See the rrdtool
man-page for details.

You could delete the 12- and 48-day RRA definions since they fall within
the 180 days you now have, but that would require a bit more work with
the source code.


> As a result of modifying that, I think as long as the 5 minute resolution 
> is stored, the zoom function would automatically pick out the 5 minute 
> resolution and use that information to render the graph, correct?

Correct.


Regards,
Henrik