We currently have use mongodb mainly to correct data and visualize with chart features. Some chart require heave disk read operation and need more performance. We need fast storage access only for analytics nodes. If we can select NVMe option only for analytics nodes, we use it but we don't want to switch whole clusters to it since main cluster don't need higher cpu/memory/stroage/iops. We just want to use NVMe only with analytics nodes. Some restriction such as min storage size for main cluster is acceptable but don't want to upgrade to higher tier of main cluster.