As a sidenote,
> As soon as you do averaging over more a longer period of time, values get
> inaccurate by the nature of RRD. This type of
> calculation is done anyway only for shadow profiles. Real profiles are
> accurate all the time, as data is read from the
> flow files. Shadow profiles do not have any data associated other than the
> RRD files for the graphs. If you need more
> accurate information for shadow profiles, you would need to extend the RRD
> layout in NfSenRRd.pm => SetupRRD.
>
> Shadow profiles come at the price of having no data assigned. This is the
> good and the bad news.
>
> - Peter
>
> Steve Foley wrote:
>> Yes, I know the RRDs will dither data over time and it does average down
>> as data ages, but I think being off by 2 orders of magnitude when I jump
>> between new data and old data (a difference of 1 day) is a bit much.
>
>> Digging through the code, I see the following in the ReadRRDStatInfo()
>> function in NfProfile.pm:
>
>> foreach my $line (@$data) {
>> my $i = 0;
>> foreach my $val (@$line) {
>> if ( defined $val ) {
>> $$statinfo{$$names[$i++]} += int(300 *
>> $val);
>> }
>> }
>> }
>
instead of parsing all the lines (I assume this code is re-used from the
way reading the 300s-interval-flowfiles works), what usually is a good
approximation for the traffic in rrd is taking the average rate for a
timeframe (which rrd will at least generate in it's graphs) and simply
multiply that by (timeframe_end - timeframe_start in seconds).
e.g. (from one of my internal, non-nfsen rrds which house 4 counters in
one rrd):
rrdtool fetch 1174242.rrd AVERAGE -r 86400 -s '04.02.2009' -e
'05.02.2009' ifInOctets ifInUcastPkts
ifOutOctets ifOutUcastPkts
1233792000: 1.8195454947e+06 2.6009227659e+03 1.5348825964e+06
2.4793893527e+03
1233878400: 1.6667955888e+06 2.4136770793e+03 1.5536676836e+06
2.4683150875e+03
looking at ifOutOctets, the average is ~1.54e+06 octets per second
(remember rrd always saves rates), multiplied by 86400 gives ~123 GB for
the day. That's not perfect, but the error is around 5% from the actual
data, and not orders of magnitude.
Kind regards,
Felix
--
Felix Schüren
Head of NOC
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