Polling Bandwidth as an Aggregate
sclark at netwolves.com
Fri Jan 20 09:59:37 CST 2012
On 01/20/2012 10:53 AM, Chris Adams wrote:
> Once upon a time, Leo Bicknell<bicknell at 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
> 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
Director of Technology
Email: steve.clark at netwolves.com
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