[Observium] Pollers and RRD files

Hi,

When using a dedicated rrd caching server - for what is the local /opt/observium/rrd caching folder used for? In our setup we created a dedicated rrd-caching server and several distributed and partitioned pollers and would expect the rrd's are only written/updated on the rrd-caching server and do not need much diskspace on the pollers but it seems the rrd's are also written on the pollers? Is that on purpose (fallback - rrd server unavailable) or what is the need of the rrd's on the pollers when using a rrd-caching server?

Thanks, Alex