[rrd-users] rrdgraph step being ignored?

[Steve Shipway]

> Now, i'm trying to graph that data (using RRDs) and for some reason, it is
> being consolidated / rendered to 90 second data points (and it should be 6
> data points in that 90 seconds).

It sounds as if RRDtool is not picking the RRA that you expect; however you
dont give us the RRD structure so there is no way to tell.

Can you post the RRD structure (rrdtool info) so that it is clear what RRAs
exist with what consolidation function, step, and length; and what the
actual Interval is on the RRD?

              "--end", "now", "-s","end-1200seconds", "--step", "15",
              "DEF:maxcap=myrrd.rrd:maxcap:MAX",

Here, you specify the start and end time as being now-(20 minutes ago) with
a *preferred* step of 15s.  You later define your DS to be of type 'MAX'.
If there is no RRA with a consolidated step of 15 and type MAX then RRDTool
will do its best to match this, either by computing a MAX summary on the
fly, or by using a different resolution RRA.  Do you really mean to graph
MAX and not AVG?

              "-w", "600",

Here, you state the graph pixel width is to be 600.  This should correspond
to 7.5 pixels per datapoint, if you have a 1200s data width with a 15s step
(thus 80 data points), which is rather chunky; but you say you instead get
only 14 data points (90s step) being displayed?  Usually, if you have >1px
per dp then RRDTool will try to get a higher resolution RRA instead; if it
is picking a lower resolution one then possibly your 15s RRA is either the
wrong type or not long enough.

Steve

Steve Shipway
s.shipway at auckland.ac.nz


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