Whether it saves space or not, looking at metrics over period of months or years when the data is raw is far more slow/expensive than looking at downsampled dat

Whether it saves space or not, looking at metrics over period of months or years when the data is raw is far more slow/expensive than looking at downsampled data. If you still want to be able to quickly graph and view old data, downsampling is the only way to keep your queries interactive. Take for instance 30s data vs 10min data. 20x more computation, network exchange and everything else of that nature needs to happen. Also if you want to keep only a subset of your data for a very long time, you need to have retention policies - otherwise you end up storing all that extra data forever. At large numbers (terabytes to petabytes) this stuff is impactful, at smaller numbers (gigabytes) my points here are far less relevant.