[rrd-users] Graphing inconsistencies graphing different time slices

Simon Hobson linux at thehobsons.co.uk
Mon Jun 8 16:58:32 CEST 2015

Munroe Sollog <mus3 at Lehigh.EDU> wrote:

> Hash: SHA1
> Very interesting.  Thank you for clarifying it.
> My problem is, as you can see from the graphing function, I am arbitrarily taking numerous rrds
> and adding them together to get a cumulative graph.  While some of these summation graphs are
> predictable, many are not; thus I can't store a cumulative rrd in all situations.

> My goal is to minimize this disparity that is caused by taking the MAX of a consolidated function.
> I am going to see if using the AVG instead of the MAX of the consolidated function will help, but
> if I really want to fix this, my only recourse is to not consolidate? I'd be storing a 1years
> worth of 1min slices for ~5000 devices.

That would be a lot of data to store, and process each time you draw a graph. Quick "finger in the air" guestimate suggests a few gigs at least. It also needs a lot of memory to make graphs.

AFAIK there is no way to consolidate a consolidation and still get an accurate MAX function, so you either have to store and work with unconsolidated data, or aggregate the data before consolidation.

It sounds like you may need to sit down and decide what's important and whether there are any simplifications you can make. Eg, if the devices naturally fall into groups, then consider if aggregating data by group would do what you want - even if the groups are dynamic in membership it's still possible to aggregate the data at the cost of more complexity in the scripts that do it.

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