Yup indeed, we have to make this more friendly because you have to curl an HTTP/JSON endpoint right now to set the configuration (we’ll release an embedded UI for policy rules editing soon, called m3ctl).

Basically though when you set retention mapping rules, metrics are downsampled to whatever resolution you choose (10s, 1min, 10min, etc) and then stored for whatever time the retention the namespace you have setup for that policy.

And with respect to my comment about disk space being the bottleneck - unless you have a huge dataset you actually might not be bottlenecked by disk, it’s just we’ve encountered that at times with our really high cardinality data sets.