Documentation

Azure Diagnostics Extension

Azure Diagnostics extension is an agent in Azure Monitor that collects monitoring data from the guest operating system of Azure compute resources including virtual machines.
It is required for VM memory utilization monitoring.

However getting such data requires single query per each VM what might cause problem if you have like 10k+ VMs. It does not have to fit into 20minutes window when LPAR2RRD collects all data.

Other metrics are collected more efectivelly, there is no necessary to make a query per each VM.