Comment 9 for bug 853955

Bruce: check out the docs for storage-aggregation.conf here: http://readthedocs.org/docs/graphite/en/latest/config-carbon.html#storage-aggregation-conf
For existing metrics, you'll need to use the utility included in whisper called 'set-aggregation-method.py'

Pablo: if you set xFilesFactor to 0, the None values will be ignored while calculating the average ( None, None, and 3 will average to 3), but values will then always propagate to the next retention rather than being dropped when less that 50% of the period has values.