It seems many users need a polling interval of less than 5 minutes. NetMRG allows tuning this interval in the main XML configuration file. However, when you set the interval to 60 seconds, you only get a day or two of high resolution data.
How might I tune the RRD aging so that I get more samples of 60-second data? From what I've read it seems like I need to grab the source and modify src/rrd.cpp. It might be nice to have a multiplier configurable from the XML which defines the number of samples for aged RRD data.
I need to see a week or two worth of 60-second data, and I know it will take a LOT more disk space. We need it to compare last week's data to this week after we made some change, and it helps a lot to have full resolution data to compare. Currently I just print out graphs before RRD ages the samples into longer timeframes.
It is our goal to have this more granularly configurable, but at the moment, you're right that rrd.cpp would be the place to look. You'll also have to tune or delete your existing RRDs.