Re: Polling Bandwidth as an Aggregate

[Steve Clark <sclark () netwolves com>]

On 01/20/2012 10:53 AM, Chris Adams wrote:
> Once upon a time, Leo Bicknell<bicknell () ufp org>  said:
> > To suggest Netflow is more accurate than rrdtool seems rather strange
> > to me.   It can be as accurate, but is not the way most people
> > deploy it.
> Comparing Netflow to RRDTool is comparing apples to cabinets; one is a
> source of information and one is a way of storing information.
>
> > RRDTool pulls the SNMP counters from an interface and records them to a
> > file.
> No, RRDTool stores data given to it by a front end such as MRTG,
> Cricket, Cacti, etc.  That front end can fetch data from any number of
> sources, including (but not limited to) SNMP.  RRDTool then stores
> information in its database.
>
> > With no aggregation, and assuming your device has accurate SNMP,
> > this should be 100% accurate.  While you are right that the defaults for
> > RRDTOOL aggregate data (after a day, week, and month, approximately)
> > those aggregates can be disabled keeping the raw data.
> RRDTool does not store the raw data.  Even for 5-minute intervals, it
> adjusts the data vs. the timestamp to fit the desired interval.  Since
> you don't read every counter at the exact time of your interval, RRDTool
> is always manipulating the numbers to fit.  The only numbers that are
> not changed before storing are the timestamp and value for the most
> recent update (which get overwritten at each update); everything else is
> adjusted to fit.
I suggest reading
http://oss.oetiker.ch/rrdtool/tut/rrd-beginners.en.html


--
Stephen Clark
*NetWolves*
Director of Technology
Phone: 813-579-3200
Fax: 813-882-0209
Email: steve.clark () netwolves com
http://www.netwolves.com