[rrd-users] rrdtool fetch: problems with resolution (returned data doesn't match param)

[Steve Shipway]

> I want to fetch data from rrd in several time resolution steps. I
> followed http://oss.oetiker.ch/rrdtool/doc/rrdfetch.en.html.
> 
> But it doesn't give back data in the precision I request (either 600 or
> 900 seconds). It simply gives back 5 minutes increments. If I set 1200
> sec as precision it the suddenly jumps to 30 minutes (1800 sec).

Are you *certain* you have an RRA of the requested resolution?  If you don't then RRDTool will use the closest resolution available.

It sounds as if you have a 5min and 30min RRA but NOT a 10min or 15min RRA.  Thus, when you ask for 10min or 15min resolution, 5min is the closest available.  When you ask for 20min then 30min is the closest so you get that.

If you want to have 10min resolution, you'll need to use 'rrdtool tune' to alter your RRD file to have an additional RRA at this resolution (probably 1cdp=2dp if you've a 5min step)

Steve

Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz
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