Hi Marc, Yesterday Marc MERLIN wrote:
> On Mon, Nov 16, 2009 at 11:21:10PM +0100, Tobias Oetiker wrote: > > > The graph definitions are in the links and the rrd was created like so: > > > /usr/bin/rrdtool create /var/lib/cacti/rra/housepower_21.rrd --step 120 \ > > > DS:HouseNoAC:DERIVE:600:-1000000000:1000000000 > > > DS:House:DERIVE:600:-1000000000:1000000000 \ > > > DS:PGE:DERIVE:600:-1000000000:1000000000 > > > DS:AC:DERIVE:600:-1000000000:1000000000 \ > > > DS:PV:DERIVE:600:-1000000000:1000000000 \ > > > RRA:AVERAGE:0.5:1:2628000 RRA:AVERAGE:0.5:1440:10950 > > > RRA:AVERAGE:0.5:5:3153600 \ > > > RRA:AVERAGE:0.5:30:525600 RRA:AVERAGE:0.5:120:131400 \ > > > RRA:MAX:0.5:1440:10950 RRA:MAX:0.5:30:525600 RRA:MAX:0.5:120:131400 \ > > > > > > I'm just trying to understand what could make these data problems > > > possible. > > > My original data on disk (before it was fed to the rrd) is correct. > > > Even if there was a time delay in when the data was given, rrdtool knows > > > how to interpolate > > > data to make things right, so I don't get it. > > > > > > Any ideas? > > > > you are talking about 'original' data, are you feeding the data to > > rrdtool INCLUDING the collection time, or are you just using N: the > > graph looks as if there was some bad case of jitter at work ... > > Sorry, I should have said that: the data is fed through cacti which does not > feed the sample time into rrdtool. So rrdtool is left with just the sample > and time at which it received it. > Samples are every 2mn so even if I had a few seconds of jitter, it should > not have made such a big difference. > > > two samples being 'faked' into one slot ... > > yes, that's pretty much what I'm seeing. > > If cacti/cron/the system were overloaded though, I would have expected to > have an empty sample and then a double sample to catch up. > I'm very perplexed here since the graphs clearly show a double sample first > and then an empty sample, which is the wrong way around. > > Does that make any sense to you? not entirely, I can only say that irregular data arrival times are rrdtools forte ... have you tried to write the data into a logfile (including the timestamp) and then recreate the phaenomenon by hand ? cheers tobi -- Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland http://it.oetiker.ch [email protected] ++41 62 775 9902 / sb: -9900 _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
