On 01/20/2012 10:53 AM, Chris Adams wrote:
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
Once upon a time, Leo Bicknell<bicknell@ufp.org> said: 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