Hi Tobias, thanks for your answer.
On 28.03.2009 17:37, Tobias Oetiker wrote: > this will not create corect results, since in GAUGE, rrdtool > assumes that for every update the value of the GAUGE datasource has > been at the new value since the last update. > > so if your updates are at irregular intervals, the updates after > long intervals wil have undue weight > > also how would you handle the case when 2 updates arrive in one > second ? The updates come irregularly but they are at least 5 minutes (300 sec) apart. And they are always on a 5 minute boundary. I *think* RRD does the following when I do my "double update": Given these datapoints time events --------------------- t_0 123 t_0 + 5m 456 t_0 + 10m 789 t_0 + 2h10m 1111 t_0 + 4h10m 2222 and this RRD --- snip --- rrdtool create test.rrd --start=1237923600 DS:events:GAUGE:600:0:U RRA:AVERAGE:0.5:1:2016 rrdtool update test.rrd '1237923899:123' # step 1 rrdtool update test.rrd '1237923900:123' # step 2 rrdtool update test.rrd '1237924199:456' # step 3 rrdtool update test.rrd '1237924200:456' # step 4 rrdtool update test.rrd '1237924499:789' # step 5 rrdtool update test.rrd '1237924500:789' # step 6 rrdtool update test.rrd '1237931699:1111' # step 7 rrdtool update test.rrd '1237931700:1111' # step 8 rrdtool update test.rrd '1237938899:2222' # step 9 rrdtool update test.rrd '1237938900:2222' # step 10 --- snap --- After step 1 the datasource events is set to 123. After step 2 the ds is set to 123 and RRD tries to build the first PDP for 1237923900. Averaging 123 (1237923899) and 123 (1237923900) gives 123. This repeats analogously for steps 3 to 6. After step 7 RRD sets the ds to 1111 but doesn't have enough data to compute PDPs for 1237924800 to 1237931400 and sets them to NaN. After step 8 the ds is set to 1111. RRD then averages 1111 (1237931699) and 1111 (1237931700) to set the PDP for 1237931700 to 1111. I'm not sure I understood the inner workings of RRD correctly. But if I did, the behavior of RRD would perfectly fit my needs. Regards -- Till -- Dipl.-Inform. Till Dörges [email protected] Senior Researcher Phone: +49 (0)700 / PRESECURE PRESECURE Consulting GmbH, Münster AG Münster, HRB 6581 Geschäftsführer/Managing Director Dr. Klaus-Peter Kossakowski CarmentiS - Early Warning Expertise http://www.carmentis.org _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
