Serge Maandag is thought to have typed the following text on Tue, 04 Jan, 2005 at 10:09:20PM +0100:
> > The output looks like: > > /usr/local/bin/rrdtool update /var/rrd/pingstats.rrd > > N:9.835:10.830:11.584:0 > > > The RRD definatly gets an integer as the fourth argument, as can be > > seen by the output from the script (which I started saving for > > debugging purposes), but how is it then possible that I > > get floats in the last GPRINTs? > > That's a question that should be added to the top of the rrdtool FAQ. > > Rrdtool normalizes all input. > You are updating using N: and that is probably not on a ( > N times step seconds since 01-01 1970 00:00:00) boundary. > Ok, since 30 pings with a 2 second interval finish in about one minute, the RRD will indeed get updated right between 2 steps (counting from 01-01-1970 00:00:00), which would explain the 6.608 for a 13% packet loss I saw. I confirmed this by generating a 53% packet loss, GPRINT shows 27.383, in both cases only a fraction more than half the actual loss. If this is indeed the case it should be mostly remedied by making the script run a minute later, or is there a better way to accomplish this? > Secondly, unless the width of your graph is exactly the same > as the amount of RRA rows you are printing, rrdtool will average > One or some rows over two adjacent pixels. This also averages your > Values and that also affects your GPRINTs. Hmmm, This is logical for the graph itsself, but IMHO shouldn't be for raw MAX and MIN calculations as in GPRINT's. A Maximum is a maximum and by definition shouldn't be averaged if it doesn't have to be for viewing purposes. BTW, am I correct in assuming that the only reason to add more RRA's with a bigger step are to minimise CPU-time at graph generation time, or am I missing something obvious here? -- Bartosz Oudekerk AOLS fortune mod volume VII Get yourself a copy at: <URL:http://www.etv.cx/~bartosz> -- Unsubscribe mailto:[EMAIL PROTECTED] Help mailto:[EMAIL PROTECTED] Archive http://www.ee.ethz.ch/~slist/rrd-users WebAdmin http://www.ee.ethz.ch/~slist/lsg2.cgi
