[rrd-users] Re: traffic volume recording

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Jan 17 18:59:46 MET 2006

On Tue, Jan 17, 2006 at 06:04:01PM +0100, Michael Bunk wrote:

> Most exact would be to read out ifInOctets once a day and calculate the 
> difference from the last day. But I actually want something more stable, eg. 
> when the counter gets reset during the day because the machine or router 
> whose traffic is monitored gets reset, I want to already have the traffic 
> volume transferred so far. Also, using COUNTER, rrdtool could handle the 
> counter wraps.

Yes, it could, unless it wraps twice in one interval.  Router resets
may look like counter wraps, unless you make sure to update the
database with U (NaN) when they happen.

> I was not clear. rrdtool update gets bytes and DERIVE should make bytes/s.

Ack.  In that case my comment isn't applicable.

Note that DERIVE does NOT deal with counterwraps.  Even worse, if you
do not set the minimum allowed rate to zero, you will get negative

> > By the way: step = 300  and  RRA:AVERAGE:0.5:288:600  means 00:00 UTC
> > to 00:00 UTC, not midnight to midnight local time.
> You mean I should watch out to use start and end time of the fetch command 
> correctly?

No, I am saying that you will not have much of a choice. Data
isn't available in any other range, only at 00:00 UTC.

If you store per hour, you can fetch midnight to midnight local time.
You also have the chance to get it right around daylight saving changes.

RRA:AVERAGE:0.5:288:600 means having 600 CDPs (intervals), each 288 PDPs
large, each CDP starting and ending at n*288*stepsize (n*86400 in your case).

Alex van den Bogaerdt

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