Cacti RRAs

RRA (round robin archive) is meant to keep recent data for high precision time and switch to bigger time aggregates for older data.
Because disk is cheap, I don't use aggregation much, see “no data loss” config tips:http://docs.cacti.net/manual:087:8_rrdtool.03_big_rra
Rrdtool graph will take the highest resolution data for any time period requested
For graphing purposes to make cacti happy, good to define weekly and monthly ranges with AVG and MAX aggregation.
Beware of the 2GB RRD file limit on 32bit systems.

RRA (round robin archive) is meant to keep recent data for high precision time and switch to bigger time aggregates for older data.