[rrd-users] changing step time?

Gregory Guthrie guthrie at mum.edu
Sat Apr 10 14:43:52 CEST 2010

Thanks, interesting..
> > "step" - specifically what happens if values are fed in more often?
> Step is the size of each bin in the database - ie the length of each
> time slot for which it can store data. Anything you feed it more
> often that the step time is accumulated until the period is complete
> and then it's all used to work out the single value stored for that
> bin.
> Eg, if you feed in values of 0,0,5,0,0 which all fit within one step
> time, then the min, max, and average are all 1.
This is a surprise! It would certainly appear at first glance that the max/min were 5 & 1.
> Alex has some excellent tutorials at
> http://www.vandenbogaerdt.nl/rrdtool/ - they explain a lot.
I'll certainly go there now, thanks.

> >2) Can I change step after the database is created?
> >   - I setup one value for daily step size, but now want to do twice-daily updates.
> >   - Can I change step size, and just start inserting updates more often?
> Don't think so. I think you have to dump the data then do one of two things :
> 1) create a new database and feed the old data in
> 2) edit the data and re-import it
My data comes from a live feed source, is there any standard way to export from rrd in a manner that allows re-import?

I suppose one could write something that would do fetches from the old, and updates into the new.

> You cannot go backwards in time. So to put historical data in, you
> must doing before putting current data in. 
Ah; so update can be backwards in time, (negative time), but all inserts must be in a forward sequence.

(Seems like these things should be in the main documentation and tutorial.)

More information about the rrd-users mailing list