On Thu, Jan 19, 2012 at 10:48 PM, Dale W. Carder <dwcarder@wisc.edu> wrote:
With the rrdtool backend, you can certainly define and add multiple sources from different files together. Using 'AREA' first and subsequently 'STACK' to view multiple data sources is particularly nice for visualization.
Except Cacti/RRDTOOL is really just a great visualization tool, while you can build stacks, it is not something that accurately meters data for billing purposes. The right kind of tool to use would be a netflow or network tap-based billing tool, that actually meters/samples specific datapoints at a specific interval and applies the billing business logic for reporting based on sampled data points, instead of smoothed averages of approximations. RRDTOOL is clearly not designed to accurately report on information for billing. To a great extent, RRDTOOL aggregates, averages, interpolates, smooths what it reports. http://oss.oetiker.ch/rrdtool/tut/rrdtutorial.en.html See "Data Resampling" Aggregation could be mitigated by including a large number of data rows at step=1 while creating the RRD file, eg for 5 minute polling 1440*(ndays) data rows; (enough rows to include the whole bill period + some number of days without aggregating), but not the rest of the issues with RRD, and including so many rows greatly increases .rrd file size. I would look at Torrus or RTG before RRDTOOL for that, but even then... If data is not gathered using a mechanism that communicates timestamp to the poller, datapoints will still be imprecise, SNMP would be an example -- the cacti application may assume the SNMP response is current data, but possibly on the actual hardware, the internal MIB on the device was actually updated 10 seconds ago, which means there will be small spikes in traffic rate graphs that do not represent actual spikes in traffic. -- -JH