[rrd-users] Fetching Data for the Finest Resolution

[Steve Shipway]

>How can I fetch the finest resolution while specifying e-2days for the start time?

If you request a given resolution then RRDtool will return it -- PROVIDED the RRD file actually has it available for ALL the requested time window.

>step = 15
>rra[0].cf = "AVERAGE"
>rra[0].rows = 244
>rra[0].pdp_per_row = 1

What this shows is that your RRD file has a 1cdp=1pdp AVG RRA (good). HOWEVER, you only have 244 rows in this RRA, and your step is 15 seconds.  So, 244x1x15=3660seconds=61minutes, the length of your RRA.  This means you can get this resolution going back in time 61 minutes, but no longer (as the data has been discarded).

If you want to get the 15s resolution back for 2 days, then you need 2x24x60x60/15=11520 rows.  In fact, safest to add several more to avoid fencepost problems.

So, extend your RRA number 0 by 11520 rows and you should be able to achieve what you want.

Steve

Steve Shipway
University of Auckland ITS
UNIX Systems Design Lead
s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>
Ph: +64 9 373 7599 ext 86487

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