Gregory Guthrie wrote: > > > "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.
RRD does not store anything but an accumulator within a step - so if you feed in those 5 values, the accumulator will hold the values 0, 0, 5, 5, 5 immediately after each update. At the end of the step, we've told it about 5 <somethings> in total, and if the step were 5 then the overall rate during the step is 1. Consolidate that with min, max, or average, and you still get 1. I think it will be clearer when you've read Alex's tutorial on normalisation. Alex van den Bogaerdt wrote: > >> 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. > >The biggest challenge is to get MIN and MAX correct. In a situation like that, you would have to accept that the data doesn't exist. In changing from a step of 1 (day, hour, whatever) to half then the only sensible way I could see would be to simply duplicate each set of values - so at time 0.5 you insert the values you had at time 1, and insert them again at time 1. Or if the rrd definition allows, just insert at time 1 and let rrdtool fill in the same value at time 0.5. The end effect is that the rrd database will hold the same rates/consolidated values from time 0 to 1 as it did before. But going forward, the new data will be processed at the higher resolution. -- Simon Hobson Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed author Gladys Hobson. Novels - poetry - short stories - ideal as Christmas stocking fillers. Some available as e-books. _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
